Bug 24165: Add ability to send any item field in a library chosen SIP field

Bug 24165: Add ability to send any item field in a library chosen SIP field

Some SIP devices need access to item fields that are not sent as item information in the checkin, checkout and item information responses.
It makes sense to allow these fields to be sent in an arbitrary and configurable way, rather than hard code in each special case.

Test Plan:
1) Apply this patch
2) Edit your SIP2 config file, add the following within the login stanza:
   <item_field field="XX" code="<item field 1>" />
   <item_field field="XZ" code="<item fied 2>" />
   where <item field 1> and <item field 2> are item table columns of your choosing
3) Using the sip cli emulator, run checkout, checkin and item information
   messages using that item.
4) Note the values you set for the item columns are sent in the
   corrosponding fields!

Signed-off-by: Jill Kleven <jill.kleven@pueblolibrary.org>
Fixed merge conflict with number of tests (was 5, changed to 7 which is correct)
Signed-off-by: Joonas Kylmälä <joonas.kylmala@helsinki.fi>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>