Bug 23913: Use a single menu to sort lists in the OPAC

Bug 23913: Use a single menu to sort lists in the OPAC

This patch modifies the sorting form on the OPAC list contents view so
that the two menus (sort field and direction) are combined into one.
This makes it consistent with the sort menu on the search results page.

To test, apply the patch and view a list with multiple titles on it.

Test the "Sort by" menu, trying all the various options. Confirm that
the pre-selected item in the sorting menu is correct after each re-sort.

Edit the list to change the default sorting and verify that the "Sort
by" menu reflects your selection.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>