Support for building most of a DMDirc jar.

Gradle can now write a version.config file properly and dumps
bundled deps into the main jar.

It doesn't yet bundle plugins, default settings, or write the
info for those to the version.config.

Change-Id: I206ff08ca2dda0aaed601a1f9f075a983eae602c
Reviewed-on: http://gerrit.dmdirc.com/4035
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Build Manager