Moved those pesky boxes behind the animation.

Also, physics::BulletPhysics bp doesn't need to be global, I guess.
GL_DEPTH_TEST needs to be enabled only once.
Renderer takes Camera as a const param.

Renderer is not allowed to make any changes to Camera.
Initial Player class implementation.

The Player class holds the camera, and the camera follows the player character.
Movement is somehow implemented, but camera rotation should be made better

e.g, so that axes don't change places.
Temp solution to camera rotation.

What this does is add a correction that is applied to camera m_up.
Skeleton and Camera controlled by the 'Player'.