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!
last vec4(cubePosition,0) to vec4(cubePosition,1) ?