fix float literals to agree with coding standard
move applyRotationDelta() from Model to JointState
move details of getJointRotation() into JointState

also: remove unused getLeft/RightHandRotation() methods
remove JointState::_translation

(use corresponding data in FBXJoint instead)
add JointState::restoreRotation()
minor cleanup + use 'fraction' instead of 'percent'