Merged in changes from development repository:

   In |purge_dc_metadata|:

      Finished this function.  Added code for updating handles associated with Dublin Core
      metadata:

          !! PLEASE NOTE:  A conservative approach is taken to modifying the handles:
          Neither the handles nor the handle values of type \.{DC\_METADATA}
          or \.{DC\_METADATA\_PID} are deleted!  Instead, handle values of
          type \.{DC\_METADATA\_DELETED} and/or \.{DC\_METADATA\_DELETED\_PID} are added
          to the existing handles.
          \par
          Since handles are supposed to be ``persistent identifiers'', they should normally not
          be deleted.  However, there is no reason not to delete or {\it handle values}, if the
          information they contain becomes out-of-date.  However, at this time, I think it's
          better to leave the old handle values and add new ones rather than replacing the old ones.
          They may be useful for searching.  This may change at some future date.