Initial Linux support

[yangosoft]

Initial compilation for Linux.
Added a CMakeLists.txt
Fixed some includes.
To compile in Ubuntu:

$ sudo apt-get install glew-utils libglew-dev libglm-dev libglfw3-dev
$ mv depends/include/glm depends/include/_glm
$ cd voxelEngine ; mkdir build ; cd build
$ make -j 8

[yangosoft]

Now builds the complete engine and the samples.

Maybe are missing some ifdef to prevent including some Windows specific header files. I just commented them.