This change also ties the plugin manager into the Wicket framework and
allows plugins to contribute and mount new pages which are linked by the
top navbar and repository navbar extensions.

This is the first step towards modularization and injection.  All
direct references to the GitBlit singleton within the Wicket pages
and panels have been replaced to proxy methods in the GitBlitWebApp
singleton.  There are still two Wicket classes which rely on the
GitBlit singleton; those require manual instantiation (servlet 3).

Change-Id: I0cdbbcf87959d590c446c99abb09c07c87c737bc

Change-Id: I9f91138b20219be6e3c4b28251487df262bff6cc

This is a massive commit which reorganizes the entire project structure
(although it is still monolithic), removes the Build classes, and
switches to Moxie, a smarter Ant build tookit based on the original
Gitblit Build classes.

The Ant build script will likely require additional fine-tuning, but
this is big step forward.

There are now three new targets on the ANT build:
- buildJAR: creates a GitBlit JAR including the GitBlit biz logic
- installMaven: install GitBlit JAR as Maven module
- uploadMaven: uploads GitBlit JAR to a Maven repository

Additional extensions have been made to allow:
a) GitBlit to load his resources outside of Wicket domain
b) GitBlit to use an injected UserService
c) Generic authentication of HTTP Request using 3rd party logic
d) Load settings programmatically from an InputStream
e) Use cookie authentication OR generic HTTP Request
   authentication for Wicket pages
f) UserModel with branch-level security logic

* Strip leading group name from repositories page.
* Put topbars on all pages.
* Properly sort repositories in all locations.
* White Gitblit logo.

Reorganization of resources. Dropped most hard-coded webapp
configuration in favor of common web.xml file. Still contemplating
configuring git servlet from web.xml too.

The JGit team is now publishing 0.12.1 artifacts on the Eclipse Maven
site. Yeah! That was the last missing piece for a slick Git:Blit
deployment. The build has been reworked to download from Eclipse and
to also download source and javadoc jars for setting up a development
environment.

Made the log4j pattern configurable by operating system.
Moved Markdown utils to their own class since I need StringUtils for
Build and that introduced a chicken-and-egg scenario.

Settings access has been abstracted and the way is becoming clear to
offer a WAR build in addition to the integrated server stack.  Util
methods moved around.

Right now the implementation is hard-coded to pass the realm into a
singleton.  This won't work for a WAR distribution so I will
need to figure out how to properly authenticate the webapp using form
authentication and the git servlet using basic authentication - host
against the same realm.