Bug 36991: Add ability to scan call numbers index/search field

Bug 36991: Add ability to scan call numbers index/search field

Some libraries ask for the ability to scan/browse the call numbers index.

Test plan:
==========
1. Have an installation with items with callnumbers (in ktd with standard
   test data set: add some callnumbers to the items).
2. Go to Advanced search > More options; choose Call number in the first
   drop list and mark Scan indexes.  Enter one of the call numbers you
   assigned to the items and perform the search.  You should get no
   results.
3. Apply the pach; restart all; when using ES:
   koha-elasticsearch --rebuild -r -d kohadev
4. Repeat p. 2.  You should get a list with at least one call number.
   The link should lead you to the record(s) with items with the selected
   call number.

This should work for ES and for Zebra, but for Zebra you would need to
replace /etc/koha/zebradb/ccl.properties with the repository version; and
you will get one token results on the list, like for other indexes.

Signed-off-by: Roman Dolny <roman.dolny@jezuici.pl>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>