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

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.

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.