Bug 29627: Map biblioitems.publishercode to 264 by default (MARC21)

Bug 29627: Map biblioitems.publishercode to 264 by default (MARC21)

This patch adds a mapping from 264 to biblioitems.publishercode.

To test:
1) Apply patch
2) Delete existing frameworks
   -  In the database
      delete from marc_tag_structure;
      delete from marc_subfield_structure;
      delete from biblio_framework;
3) Load default framework
   - In a terminal, run
     ./misc/load_yaml.pl -f installer/data/mysql/en/marcflavour/marc21/mandatory/marc21_framework_DEFAULT.yml --load
4) In the staff interface, go to Administration > MARC bibliographic framework
   - Make sure the default framework is there
5) In Administration > Koha to MARC mapping, check the mappings for biblioitems.publishercode
   - biblioitems.publishercode should be mapped to 260 as well as 264
6) Create a bibliographic record with a value in 264
   - In the database, check the biblioitems entry for this record, the value from 264 should be in publishercode
7) Create a bibliographic record with a value un 260
   - In the database, check the biblioitems entry for this record, the value from 260 should be in publishercode

I hope I didn't forget anything! :)

Caroline

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>