Added a short term ingame configuration gui

From what I know @bspkrs will be doing the ingame configuration gui, but that won't be anytime soon because he's working on the MCPBot database. This is not the best gui, but should be good enough until we get a proper one.

http://puu.sh/agKnK.png

The list of mods is populated only with mods that have a valid ``IModGuiFactory`` implementation.