Bug 5810: Subject tracings search complete subfields

Bug 5810: Subject tracings search complete subfields

This patch adds the syspref TraceCompleteSubfields. When TraceCompleteSubfields
is set to "force," clicking on links in non-authority controlled subject
tracings will only find other records where the entire subfields match. Leaving
it at "don't force" keeps the current behavior of doing a keyword search of the
subject indexes.

This patch implements complete-subfield subject tracings in MARC21 XSLTs (OPAC
and Staff) and all Normal mode interfaces. UNIMARC XSLTs have not been updated.

This patch also adds the syspref UseAuthoritiesForTracings. When set to "Do not"
tracings in the XSLT detail displays will never generate links using authority
numbers, but rather use the heading strings (NB: the tracings currently use only
subfield 'a' for generating links).

Signed-off-by: Nicole C. Engard <nengard@bywatersolutions.com>
Signed-off-by: Jane Wagner <jwagner@ptfs.com>
Signed-off-by: Jared Camins-Esakov <jcamins@bywatersolutions.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>