Bug 17233 - Add 008 value builder plugin for MARC21 classifications

Bug 17233 - Add 008 value builder plugin for MARC21 classifications

This patch adds 008 cataloguing value builder for MARC21 classifications
records (LCC, DDC/Dewey, UDC and so on).

For most practical purposes, MARC21 classification records
(<https://www.loc.gov/marc/classification/>) are quite similar to regular
MARC21 authority records, so handling them in Koha is (almost) achievable
by means of the built-in 'regular' MARC21 authority records related
functionalities, but there are some notable differences - in particular,
008 field length and format is not the same.

To test:

1) apply patch
2) link the new plugin (marc21_field_008_classifications.pl) to the 008
field in the existing (or cloned, ..) authority framework of your choice
3) try to add, edit, re-edit 008 field using this "authority" framework,
ensure that the new plugin behaves as it should according to the
Library of Congress specifications for MARC21 classification records
008 field format (<https://www.loc.gov/marc/classification/cd008.html>).

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>