LDAP SSH key manager

Fixes the build that was broken by cherry-picking commit 2be2c2,
which resulted in an import collision on the `SecureRandom` class.

Secure cookies

Introduce our own wrapper `SecureRandom` around `java.security.SecureRandom`.
This a) makes sure that the PRNG is seeded on creation and not when
random bytes are retrieved, and
b) uses a static instance in the `UserModel` so that lags do not occur
during operation due to potentially seeding getting blocked on Unix
when reading from the system's entropy pool. To keep the random data
still secure, the static instance will reseed all 24 hours, also a
functionality of the wrapper class.

This fixes #1063 and extends and closes PR #1116

The regular expression used for user mentions used to work
only inside sentences. Also, since it tested for whitespace, the
whitespace would get replaced, too, which would join lines together.

Instead the new regex uses boundary matchers to match against
word boundaires. As these are not capturing only the actual user
mention can be captured and is then replaced. Also, this way the
regex can ignore punctuation like in "@jim, look at this."

Since Gibtlit now requires Java 7 we can use named capture groups.
This makes the use of a centrally defined regular expression much
safer. The (admittedly only) group to capture the user name is named
"user" and can be referenced by this name. By using the name instead
of a group number, the regex could be changed without the code using
it breaking because the group number changed.

A simple test is added for user mentions, which unfortunately
has to deal with the full markdown replacement, too.

Fixes #985

So far for session cookies the secure property was only set when no
HTTP port was opened. This changes to also set it when HTTP is redirected
to the HTTPS port.

Mark the user authentication cookie to be only used for HTTP, making
it inaccessible for JavaScript engines.


If only HTTPS is used and no HTTP (i.e. also if HTTP is redirected to
HTTPS) then mark the user cookie to be sent only over secure connections.

Some public key mangers may be read-only, i.e. not allow to add or
delete keys, or to change the key comment or assigned permissions.
In such a case the respective commands should not be available on the
SSH shell and the SSH Keys panel should also not offer the possibility.

The `IPublicKeyManager` gets three new methods, modelled after the
`AuthenticationManager`:
`supportsWritingKeys`, `supportsCommentChanges` and
`supportsPermissionChanges`. They return true if a key manager allows for
keys to be written or updated.
For example the existing `FileKeyManager` will return true for all three
since it allows to store and update keys in a file.
The new `LdapKeyManager` returns false since it only accesses LDAP and
can not add or update any keys in the directory.
A future key manager might get keys from an LDAP directory but still
keep comments and permissions for it in a local copy.

If writing of keys is not supported:
* the welcome shell does not suggest adding a key,
* the `SshKeysDispatcher` does not offer the "add", "remove", "comment" and
  "permission" commands, and
* the SSH keys panel hides the "delete" button in the key list, and the
  "Add Key" form.

The hiding of the "Add key" form is not perfect since the surrounding
div is still shown, but I don't know how to hide it and it didn't look
too bad, either.

The `SshKeysDispatcher` tests that use the keys list command are failing
on Windows because they assume a Unix line ending after each key. But
the command will use a system line ending. So this fix uses system line
endings in the reference string for the assert, too.

In addition, two `assertTrue(false)´ are replaced with a proper `fail`.

Instead of using fixed ports for the listeners of the in-memory
LDAP server, let the listeners select ports and then save them in
the authentication mode instance. This way we prevent port collisions,
which especially showed up under Windows.

Make the SSH authentication methods used by the server configurable,
so that for example password authentication can be turned off.

For this, a `git.sshAuthenticationMethods` setting is added which is a space
separated list of authentication method names. Only the methods listed will
be enabled in the server.
This is modeled after the option of the same name from sshd_config, but it
does not offer listing multiple required methods. It leaves the door open,
though, for a later extension to support such a multi-factor authentication.

Since this also includes Kerberos authentication with GSS API, this obsoletes
the `git.sshWithKrb5` property. The latter is removed. Instead, to enable
Kerberos5 authentication, add the method name `gssapi-with-mic` to the
authentication methods list.

Add new class `LdapPublicKeyManager` which retrieves public SSH keys
from LDAP.

The attribute can be configured with the new configuration option
`realm.ldap.sshPublicKey`. The setting can be a simple attribute name,
like `sshPublicKey`, or an attribute name and a prefix for the value,
like `altSecurityIdentities:SshKey`, in which case attributes are selected
that have the name `altSecurityIdentities` and whose values start with
`SshKey:`.

Extract the inner class `LdapConnection` from the `LdapAuthProvider`
into a separate class, so that it can be used from multiple classes
that have to connect to an LDAP directory.
The new class is placed into the new package `com.gitblit.ldap`, since
it isn't specific to authentication.

Extract the creation of the in-memory servers and the interceptor
code to a base class that LDAP related unit tests can extend to
have the servers available.

Set "can admin" permission on LDAP users and teams correctly

The canAdmin permission is set on a LDAP user, when the user is listed
in `realm.ldap.admins` or is a member of a team listed in `realm.ldap.admins`.
This leads to inconsistent and surprising behaviour on the EditUser page
when clicking the "can admin" checkbox. Also, the "can admin" checkbox
is disabled, but not checked, for teams that are listed as admin teams.

The new behaviour implemented in this patch makes users and teams from
LDAP match local ones. That means:
* LDAP teams that are listed in `realm.ldap.admins` get the canAdmin
  property set if teams are maintained in LDAP.
* LDAP users that are listed in `realm.ldap.admins` get the canAdmin
  property set if teams are maintained in LDAP.
* LDAP users do not get the canAdmin property set, if they are only a
  member of a team listed in `realm.ldap.admins`.
* The `supportsRoleChanges` method for users and teams of the
  `LdapAuthProvider` unconditially returns false if teams are
  maintained in LDAP, not only for users and teams listed in
  `realm.ldap.admins`.
* Therefore, for all LDAP users and teams the "can admin" checkbox
  is always disabled if teams are maintained in LDAP.

Fix disabled links in PagerPanel

Fix LDAP binding strategies

Extend the comments for some realm.ldap.* properties to better explain
use cases and requirements.

Gitblit allows in its configuration to set a "manager" user (and password) which can be used
to search for the entry of a user wanting to log in. If they are both not set, an anonymous search
is attempted. In the description below, when I say "...as manager", it is either as manager or
anonymous.
So far the behaviour of Gitblit, with respect to binding to and searching in LDAP,
has been the following when a user logs in:

**bind as manager**
**search for the user**
_bind as the user_
_search for the teams_

I'll call this code flow A.

Later an additional configuration option had been added: `realm.ldap.bindpattern`.
(PR gitblit/gitblit#162) It was meant to allow for not using a manager nor anonymous binds,
by searching the directory as the user logging in.
This is done in code flow B:

**bind as manager**
_bind as user_
_search for user_
_search for teams_

Both A and B are flawed, I think. In A, it looks like a mistake to me that the binding stays with the
user after authentication. The problem that this causes is, that in LDAP server configurations
where normal users are not allowed to read groups, the team information cannot be retrieved.
I tried but failed to understand how B is supposed to work. There will always be a bind request
as either anonymous or the manager DN when the LDAP connection is created. If neither is
possible, the authentication process will fail and the user cannot log in.

When synchronizing users and teams from LDAP, the following code flow is exercised:

F:
**bind as manager**
**search for users**
**search for teams**

This patch fixes both code flows by introducing a new flow.

C:
**bind as manager**
**search for user**
_bind as user to authenticate_
**bind as manager**
**search for teams**

And it changes code flow B to the following code flow D:

_bind as user_
_search for user_
_search for teams_

With code flows A, C, D and F the following usage (and authentication) scenarios are covered.
They are described from the view of a Gitblit administrator's intent and his LDAP setup.

* Users and team should be snychronized with LDAP
	This means anonymous or a fixed account must be able to read users and groups.
	=> covered by C and F

As the above allows for authentication and is required for synchronisation, all the others below
do not cover synchronization.

* No anonymous binding allowed and no special manager binding required
	This means that users must be able to read user an group entries.
	=> covered by D

* The user DN needs to be searched, e.g. because they are not all under the same parent DN.
	This means that anonymous or a fixed account must be able to read users.
		-- anonymous or the "manager" account can also read groups
			=> covered by C
		-- anonymous or the "manager" account cannot read groups but a user can
			=> covered by A

I therefore believe that the new code will cover all common use cases. The implementation
either directly binds as the user, when `bindpattern` is not empty, or it binds anonymous or
against the manger DN to search for the user DN entry.

If it directly bound against the user DN, the user is already authenticated. It will then only check
that the user DN it found in the search is identical to the one it is currently bound against. If it
was bound against a manager DN (or anonymously) it will bind against the found user DN to
authenticate the user logging in, and will then rebind against the manager DN.

When searching for groups in LDAP, if the search fails with a result code other than SUCCESS,
the implementation will bind against the user DN, if it isn't already bound against it. It will then
repeat the search for groups under the user authorization. This is to keep backwards
compatible with the original behaviour A, in order to not break cases where the LDAP setup
would deny a manager account to search for groups but allow it for normal users.

To achieve this the implementation introduces an internal `LdapConnection` class that wraps
the connection and keeps bind state, so that a rebind as a user is possible.
This also fixes a resource leak where the connection was not closed in case that the initial bind
as the manager account did not succeed.

This commit would fix gitblit/gitblit#920

Add access restrictions to the LDAP test server instances.
New modes used a test parameters are ANONYMOUS, DS_MANAGER and USR_MANAGER.
ANONYMOUS can bind anonymously and access users and groups.
In DS_MANAGER the server requires authentication and will only allow
the DIRECTORY_MANAGER user to search for users and groups.
In USR_MANAGER only the user can search groups, the USER_MANAGER, which
is used to bind in this mode, can not.

A third server instance is created because I did fear side effects should
the tests be run in parallel, had I tried to configure the access
restriction in Before.

Instantiate two LDAP servers, one that allows anonymous access, and
one that requires authentication for all operations.
The JUnit test is parameterized to run all tests with both instances.
It uses different settings for each mode.

Disabled links in the PagerPanel (used on the LuceneSearchPage to page
through search results) were only rendered as "disabled". The links
themselves remained active, which gives strange effects when clicked.
For instance it was possible to move to result pages -1, -2, and so on.

Really disable the links. Add missing CSS rules to have correct styling
as Wicket renders disabled links as spans, not anchors. Include the new
CSS file in BasePage.html. And add the left/right arrows only if not on
the first/last page.

Improve logging when sending email fails.

Merge strategy

The merge type is a per repository setting. Add it to the edit page.

Add the option to merge a ticket branch to the integration branch
only when it can be fast-forwarded, or
always with a merge commit, or
by fast-foward if possible, otherwise with a merge commit.

Adds a new property ticket.mergeType with the valid values
FAST_FOWARD_ONLY, MERGE_ALWAYS and MERGE_IF_NECESSARY.

Merging and canMerge were refactored to make use of a new
IntegrationStrategy class for each type of strategy.

Issue #1076: load commit cache in a background thread

* Make the CommitCache fully thread-safe. It was using a
  ConcurrentHashMap containing lists, but then handed out these lists.
  It also did multiple operations on that map that as a whole should
  be atomic.
  
* Use isEmpty() instead of size() == 0.

* Run the loading of the commit cache in a background daemon thread

Spelling mistake fix

pushedNewBranch was wrongly spelled

1.8.x tranditional chinese translation

Fix &rt; to > in mail (in rename status line)

fixes #1104

Fixes #964 - add missing redirect after restoring user in new session