Bug 22544: Refactor searching of news items

Bug 22544: Refactor searching of news items

Test plan:
1) Go to tools and define some news
2) Try different parameters, try to edit new items, and delete some
3) Go to all places where news are presented and ensure that there are
the right ones shown:
    opac main page - based on language
    opac righ column (formerly syspref OpacNavRight) - based on language
    opac news rss feed
    circulation slip (not quick slip)
    intranet main page
4) run tests:
prove t/db_dependent/Koha/News.t

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>