CAS-1439: PGT and PT ids should begin with their assigned prefix

Supersedes https://github.com/Jasig/cas/pull/420

Issue https://github.com/Jasig/cas/issues/482 and https://github.com/Jasig/cas/issues/483
by moving this here are we allowing subclasses to match(i.e. if a TGT and an ST object got the same id, this would say they are equal correct?)