use @Parent annotation in UserLogEntryDao to ref UserDao
perform referential integrity check on entity deletion

-define new annotations @InboundRef and @InboundRefs
-in onDeleteDao, call checkForInboundRefs(DAO)
-in checkForInboundRefs(DAO), query for inbound refs in designated
entities and throw IllegalStateException if any are found.
-fix default unapplied job pct in GaeRule to be 0, not 100
Merge pull request #46 from adennie/delete-ref-check

Delete ref check