Add attribute locations for GPU programs.

- 0: in_Position
- 1: in_TexCoord0
Shaders can now be enabled/disabled.
Implement Shader::setMatrix4 member function.
Create a global logger.
Add macros for easy logging.
SystemLogOutput flushes its buffer at every calls.
Enhance Sprite::loadTexture.
Sprites now load their textures at construction.
Implement initialization of sprites VBOs.
Implement void Sprite::draw() function.
Implement Sprite's destructor.
Update "basic" shader for texturing support.
Change Game class to debug sprites.
Merge branch 'master' of github.com:antoine1fr/Rage-Of-Street