Bug 21979: Add option to SIP2 config to send arbitrary item field in CR instead of...

Bug 21979: Add option to SIP2 config to send arbitrary item field in CR instead of collection code

Some libraries need to send a different field as the collection code,
depending on how the library catalogs items. We should allow any arbitrary
item field to be used as the value for the CR field.

Test Plan:
1) Apply this patch
2) Set the new option cr_item_field to 'shelving_location'
3) Restart the SIP server
3) Perform a checkin via SIP
4) Note the CR field contains the shelving location code in the response
5) Perform an item information request
6) Note the CR field contains the shelving location code in the response

Signed-off-by: Jesse Maseto <jesse@bywatersolutions.com>
Signed-off-by: Bouzid Fergani <bouzid.fergani@inlibro.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>