Bug 5957: Making COiNS in OPAC search results optional

Bug 5957: Making COiNS in OPAC search results optional

Adds a new system preference, COinSinOPACResults, which toggles the inclusion of
COiNS/OpenURL/Z39.88 in the search results display.  Default is 'on', continuing
the current behaviour.

Disabling this feature will result in a significant increase in search speed, since
each call to GetCOinSBiblio requires a separate parsing of the MARC record, and there are
<OPACnumSearchResults> calls to this routine with each search.

Signed-off-by: Jared Camins-Esakov <jcamins@bywatersolutions.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>