adding "locks" to Registry.update and "lock" Registry.getitem_reset
adding rejester.exceptions.LostLease
adding --runperf to make test
making the "dict_Name"_locks used by .update() the same structure as a 1to1 mapping
making an abstract base class for Worker

making WorkUnit.update raise LostLease when it should

cleaning up HeadlessWorker/MultiWorker

need more tests