Bug 13757: Add the option to set patron attributes editable in the OPAC

Bug 13757: Add the option to set patron attributes editable in the OPAC

Note: this is a squashed version of the original patchset, because it was needed

This patch adds an opac_editable property of borrower attribute types
that can be set in the interface. I'm removing work on OPAC and will
refactor it, keeping the author attribution.

Test plan:
  1. Repeat the following with a new and existing borrower attribute
     type:
  2. Verify that "Editable in OPAC" can only be checked if "Display in
     OPAC" is checked.
  3. Verify that this new property is correctly saved.

Signed-off-by: Aleisha <aleishaamohia@hotmail.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>