Add EntityManager (which contains the main loop)
Note : the FMOD sound test doesn't work anymore ; just wait for the FMOD facade...
Add PhysicalEntity
Add PhysicalManager
Note : it is contain by the GameManager
Correspondance between lists of RenderEntity and PhysicalEntity
Note : the pattern composite is OK !
Warning : it's OK if the rabbits disappear in few secondes... (due to box2d tests)