Removed superfluous caching from Camera.
Optimization: FacingObject now uses Vector3D constants.
Remoevd superflouous position setting in RotateAroundObject.
Bugfix: Rotate and Facing activated in wrong order in BriefingScreen.
Bugfix: Camera matrix state not updated at same time as other GPU
states.
Bugfix: Thread deadlock in ThreadManager for pending GPU mem access
tasks.