BibEdit: send latest timestamp when reverting

* Modifies 005 tag of record to be reverted to match the latest timestamp
  available.

Reported-by: Mike Sullivan <sul@slac.stanford.edu>
Signed-off-by: Javier Martin Montull <javier.martin.montull@cern.ch>
Reviewed-by: Samuele Kaplun <samuele.kaplun@cern.ch>