Liquidfun support (Box2D particles)

Hey,
I added support for the open source liquidfun library made by Google. If you don't know about it here you can get some information: 
http://google.github.io/liquidfun/

I added the C++ code (If you wonder why all Box2D files are edited: I was a bit lazy so I just threw all liquidfun files, which are the original Box2D files + particles, into libgdx and added the lines written by libgdx developers) and some java classes so you can access the particlesystem. I also wrote a debug renderer and one fluid renderer, but I excludet the last one because I don't liked it too much (I'm pretty new to GLSL so I wasn't able to archive the result that I aimed for)

Nevertheless here are some pictures:
http://www.directupload.net/file/d/3500/4b9yidra_png.htm (This one is taken from the LiquidFunTest class)
http://www.directupload.net/file/d/3500/b2xdsxlb_png.htm
http://www.directupload.net/file/d/3500/4gfk97dc_png.htm

The performance is very good already, I can simulate more than 15000 particles with constant 60 fps. But there are still some performance improvements possible. Probably I will work on them later...