Force a new writing system id when duplicating

Duplicating an existing writing system in the UI, then deleting the
duplicate would result in deleting the original writing system since
the duplicate has the same id with a simple Clone based duplication.
Some of the needed information (list of current writing systems that are newly created and not yet stored in the repository) is available only locally where the change currently is made.  So adding a new method would require changing the code in two places.  That might be the right answer, but I'm not sure how often a new method would be used.