Bug 21336: Search, lock and anonymize methods

Bug 21336: Search, lock and anonymize methods

Add Koha::Patron->lock and anonymize.
Add Koha::Patrons methods search_unsubscribed, search_anonymize_candidates
and search_anonymized. And wrappers for lock and anonymize.
Add unit tests.

Test plan:
Run t/db_dependent/Koha/Patrons.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>