Bug 20517: Use the "sort bin" field in SIP2 Checkin Response

Bug 20517: Use the "sort bin" field in SIP2 Checkin Response

This bug adds the SIP2SortBinMapping to make it possible to tell
the Koha SIP2 server to include a sort_bin/CL field in the
Checkin Response, if appropriate.

To test:
- Check out an item and return it via SIP2:
  $ telnet localhost 8023
  9300CNterm1|COterm1|CPCPL|
  09N20200422    12430020200422    124300APCPL|AOCPL|AB001|AC|
  (Where 001 in |AB001| is the barcode of the item in question)
- Check there is no CL field in the last response
- Apply the patch, fill in SIP2SortBinMapping with e.g.:
       CPL:itype:BK:3
- Repeat the first step
- Check the respons contains a CL field with a value of 3 (or what
  you put in the config). The field should look like |CL3|
- Signe ye offe

2020-06-25: Pass an item to _get_sort_bin, not a checkout. Rebase.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>