Bug 25871: Add "only library" to OpacItemLocation options

Bug 25871: Add "only library" to OpacItemLocation options

This patch adds a new option to the OpacItemLocation system preference,
"only library." It also rewords the descriptions of the existing options
in order to make their use more clear.

To test, apply the patch and make sure your OPACXSLTResultsDisplay
system preference is set to "default."

Test the OPAC search results using each of the OpacItemLocation
preference options:

- location: "library, location, and call number," e.g.

  "Availability: Items available for loan: Athens (1).
   Location(s): Athens new book shelf Call number: JNF 952.025 Bl."

- ccode: "library, collection code, and call number," e.g.

  "Availability: Items available for loan: Athens (1).
   Collection(s): Juvenile non-fiction Call number: JNF 952.025 Bl."

- callnum: "library and call number," e.g.

  "Availability: Items available for loan: AthensCall number: JNF
   952.025 Bl (1)."

- library: "only library," e.g."

  "Availability: Items available for loan: Athens (1)."

Signed-off-by: Amit Gupta <amit.gupta@informaticsglobal.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>