Wip/texturing cube

Working well with CubeDirt and CubeSand. 

TODO: clean code

Do we have to unbind the vao and rebind it? 
file: testCubeGLInstancedRendering.cpp 
line: 131

I will check after LE FOIE GRAS!
relative path: at runtime you're in build/bin/... where there is build/bin/assets/textures/dust.png