Bug 32911: Remove ILL partner_code config from koha-conf.xml and turn it into a syste...

Bug 32911: Remove ILL partner_code config from koha-conf.xml and turn it into a system preference

Preparation:
1) apply patch
2) run reset_all
3) enable ILLModule sys preference
4) install a backend (e.g. FreeForm)
5) go into system preferences and confirm that ILLPartnerCode exists and is the default inter-library loan (IL)

Test plan:
1) create an ILL request
2) ensure the patron of category 'IL' has a primary e-mail configured
3) click on "place request with partners"
4) verify that the patron(s) of said category are on the partners list

Upgrade test:
1) Remove the system preference from the database, run query:
delete from systempreferences where variable="ILLPartnerCode";
2) Check or edit the value or partner_code in koha-conf.xml and run atomicupdate:
installer/data/mysql/updatedatabase.pl
3) Confirm the value in koha-conf.xml has been successfully migrated into the system preference, run query:
select * from systempreferences where variable="ILLPartnerCode";

Optional tests:
- Set a patron category in the sys pref and then delete said patron category (needs to not have patrons in it)
- Check the about page -> System information and confirm the warning message is correct

- Set the sys pref to the empty option
- Check the about page -> System information and confirm the warning message is correct

- Set the sys pref to a category that has no patrons of its type (ktd examples: Board, or Library)
- Check the about page -> System information and confirm the warning message is correct

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>