Bug 11334: add ability to control which library fields are used for facets

Bug 11334: add ability to control which library fields are used for facets

The current "Library" facet is somewhat ambiguous for Koha installations
with multiple libraries. It refers to the holdingbranch, but does not
explicitly state this. It would be beneficial to allow the administrator
to choose to show facets for the holding library, home library, or both.
In addition, the facets should be more explicitly labeled.  This patch
adds this flexibility.

Test plan:
1) Apply this patch
2) Check that the facets label "Libraries" now reads "Holding libraries"
3) Update the system preference DisplayLibraryFacets to "home library"
4) Check that the facet now reads "Home libraries"
5) Update the preference again to "both home and holding library"
6) Check that both the facets for home and holding library are now
   displayed.

Signed-off-by: Jen DeMuth <jdemuth@roseville.ca.us>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Passes all tests and QA script.
Changes apply to both prog and bootstrap OPAC and staff client.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>