Bug 18911: Add the ability to set the preferred lang for notice at the OPAC

Bug 18911: Add the ability to set the preferred lang for notice at the OPAC

Patron should be allowed to modify this setting without asking a staff
member.

The setting is not configurable and cannot be hidden via a syspref.

Test plan:
- Turn the pref TranslateNotices on
- Install some languages
- Edit your messaging settings at the OPAC
=> Notice the "Preferred language for notices" dropdown list
- Select one
=> Confirm that the value is saved in DB

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>