Bug 24254: Implement separate filters and add patron param

Bug 24254: Implement separate filters and add patron param

This patch introduces two new methods for stacking filters on
Koha::Items:

- filter_out_lost
_ filter_out_opachiddenitems

This two filters are what actually happened inside the
filter_by_visible_in_opac. Everything is covered by tests.

In the process I added a Koha::Patron param to the method that is
internally used to decide if the OPACHiddenItems syspref needs to be
honoured or not. This *could* be better done with a fallback to
C4::Context->userenv if no param is passed.

I decided to leave that part for later, if we really find it would help
(e.g. if bug 10589 gets some action and we really need something here to
 handle that).

To test:
1. Apply this patch
2. Run:
   $ kshell
  k$ prove t/db_dependent/Koha/Items.t
=> SUCCESS: Tests pass!
3. Sign off :-D

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>