Bug 12567: Make catalog statistics wizard publication year work for MARC21

Publication year was useless for MARC21, as it was using the
biblioitems.publicationyear (UNIMARC) instead of biblio.copyrightdate
(MARC21).

This patch tries to fix the search options to work for both MARC
flavours.

To test:
In Reports > Statistics wizards > Catalog:
- Test the publication year search options on a UNIMARC and
  a MARC21 installation.
- Make sure search results make sense for both.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
The changes are fine with me, but this script is certainly not bug free.
Also note that all its SQL should be moved out according to our
coding guidelines. When doing so, a rewrite would be appropriate.

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>