BaseAuthzGroupService/BaseAuthzGroup have various old-style code that could be cleaned up.

#1: This pair make use of a "private agreement" that their mutual classes can still be resolved even after a round trip to the ComponentManager. In particular the following line of code

if (m_lazy) ((BaseAuthzGroupService) (AuthzGroupService.getInstance())).m_storage.completeGet(this);

is repeated over a dozen times in the BaseAuthzGroup, which would be an impermissible cast if https://sakaiproject.atlassian.net/browse/SAK-12166#icft=SAK-12166 and following went ahead. It would also actually be a small performance improvement if the service were simply injected in the constructors to the group object since we would not incur the locking overhead of a CM trip.

#2: Various Java 5 updates - use of generic collections both in impl and API improve readability and type safety.