Add dependent libraries

Build various libraries needed by GamePlay.

This will allow the building of libs on all platforms supported by GamePlay.  The most notable change is that everything has moved away from being library specific.  No more "lua/include" or "bullet/include".  Instead there's a single "include" directory.  There's also a single static archive produced: libgameplay-deps.a or on Windows gameplay-deps.lib.  This will allow for the easy addition of libraries in the future without trashing everyone's build system.  But right now, it means having to modify project files in GamePlay to work with the new system.