EST-155: made status not optional; WithStatus renamed to WithLockable as JDO workaround

... see the Javadoc comment in the WithLockable interface.
ISIS-155: status now mandatory; renamed LeaseUnit to Occupancy; minor improvements on Numerator

* Status is now mandatory everywhere
  - nb: Api#putLeaseItem and Api#putLeaseTerm now require the status to be provided.

In addition:
-