Changes contain:
- Making rsGroupInfoManager non-static in RSGroupAdminEndpoint
- Encapsulate RSGroupAdminService into an internal class in RSGroupAdminEndpoint (on need of inheritence).
- Change two internal classes in RSGroupAdminServer to non-static (so outer classes' variables can be shared).
- Rename RSGroupSerDe to RSGroupProtobufUtil('ProtobufUtil' is what we use in other places). Moved 2 functions to RSGroupManagerImpl because they are only used there.
- Javadoc comments
- Improving variable names
- Maybe other misc refactoring
Change-Id: I09f0f5aa413150390c91795b8a8fd5e6cdd6c416