* Santiation fix from Gogs

* Linting

* Fix build-errors

* still not working

* Fix all the things!

* gofmt

* Add code-injection checks

* initial stuff for oauth2 login, fails on:
* login button on the signIn page to start the OAuth2 flow and a callback for each provider
Only GitHub is implemented for now
* show login button only when the OAuth2 consumer is configured (and activated)
* create macaron group for oauth2 urls
* prevent net/http in modules (other then oauth2)
* use a new data sessions oauth2 folder for storing the oauth2 session data
* add missing 2FA when this is enabled on the user
* add password option for OAuth2 user , for use with git over http and login to the GUI
* add tip for registering a GitHub OAuth application
* at startup of Gitea register all configured providers and also on adding/deleting of new providers
* custom handling of errors in oauth2 request init + show better tip
* add ExternalLoginUser model and migration script to add it to database
* link a external account to an existing account (still need to handle wrong login and signup) and remove if user is removed
* remove the linked external account from the user his settings
* if user is unknown we allow him to register a new account or link it to some existing account
* sign up with button on signin page (als change OAuth2Provider structure so we can store basic stuff about providers)

* from gorilla/sessions docs:
"Important Note: If you aren't using gorilla/mux, you need to wrap your handlers with context.ClearHandler as or else you will leak memory!"
(we're using gorilla/sessions for storing oauth2 sessions)

* use updated goth lib that now supports getting the OAuth2 user if the AccessToken is still valid instead of re-authenticating (prevent flooding the OAuth2 provider)

This change corrects a few logging issues:

 * Standardized formatting errors with '%v'.
 * Standardized failure warning word usage.
 * Corrected an instance of using the standard log library when
   the gitea log library should be used instead.

* Allow custom public files

* Gofmt code, lots of places not related to this pr

* New settings option for a custom SSH host (#3763)

* let default ssh listen addr empty

Integrated optional bindata for the templates

* Get rid of the bin folder within the build process

Signed-off-by: Thomas Boerger <thomas@webhippie.de>

* Dropped latest make task, it is unused

Signed-off-by: Thomas Boerger <thomas@webhippie.de>

* Added tidb tag to drone config

Signed-off-by: Thomas Boerger <thomas@webhippie.de>

* Dropped the cert build tag

Signed-off-by: Thomas Boerger <thomas@webhippie.de>

* Dropped useless minwinsvc build tag

Signed-off-by: Thomas Boerger <thomas@webhippie.de>

* Dropped the useless build tags from drone config

Signed-off-by: Thomas Boerger <thomas@webhippie.de>

* move init functions from routers/install to routers/init

* copyright typo