Bug 21249: (follow-up) Fixing syspref name, description, get working with OPAC masthe...

Bug 21249: (follow-up) Fixing syspref name, description, get working with OPAC masthead search

Syspref is now called SearchLimitLibrary, and the description better
explains what the feature does. It works with the advanced search on the
staff client and OPAC, and the masthead search on the OPAC when
OpacAddMastheadLibraryPulldown is enabled.

Sponsored-by: Catalyst IT
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: David Cook <dcook@prosentient.com.au>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>