Bug 7617: Sort authority results by authid

Add the option of sorting authority search results by authid, and instruct the
FirstMatch and LastMatch linkers to use that sort order rather than the default
search order.

To test:
1. Install new Zebra authorities config
    etc/zebradb/marc_defs/marc21/authorities/authority-koha-indexdefs.xml,
    etc/zebradb/marc_defs/marc21/authorities/authority-zebra-indexdefs.xsl,
    etc/zebradb/marc_defs/marc21/authorities/record.abs, and
    etc/zebradb/marc_defs/unimarc/authorities/record.abs
2. Reindex authorities in Zebra
3. Set LinkerModule to FirstMatch or LastMatch
4. Add two identical authority records, and a bib record with a heading that
   matches them
5. Run misc/link_bibs_to_authorities.pl on that record
6. Confirm that the authid that's been inserted into subfield $9 of that
   heading is the first, if you selected FirstMatch, or last if you selected
   LastMatch

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
I followed the test plan and checked that for "Last match" and "First match"
the correct authority was selected and linked to the record.

Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>