Flag to configure UNIFYBroker/Plus to delete adapter entities with incomplete joins

If an adapter has an incomplete entity on a link (i.e. no matching locker entity for the join criteria) then currently UNIFYBroker reports a warning.  In many circumstances it would be appropriate to delete the adapter entity in this situation, to ensure the external data source was kept in sync with the locker.  Add a configuration flag to enable this functionality.