Added MessageSystem with several classes
Switched SceneNode to Component. Deleted references to scene
New System used for (Physical-)SceneNode. More to come
New System used for Light
MessageReceiver requires HAS-A
New System used for RigidBody. Rework needed

Split PhysicsWorld and Scene.
PhysicsWorld keeps reference at btRigidBody and SceneNodes at once
Additional to previous commit
Corrected relations (HAS-A _ IS-A)
Fixed Bug. Velocities can be set
Parted Scene and World. RigidBody has no use anymore
Renamed class World to PhysicsWorld
Oculus Dist works for 1280x800. StereoCamera does not...
Fixed bug of not resetting OGL after Rift render