BibRank: no citerank error when no citations

* If no citations are available, citerank methods should
  silently exit.  (closes #1624)

Reviewed-by: Tibor Simko <tibor.simko@cern.ch>
BibField: fix number_of_copies field

* Fixes problem with numbers_of_copies field definition
  which fixes also recjson cache recreation.  (closes #1625)

Reported-by: Theodoropoulos Theodoros <theod@lib.auth.gr>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>
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>