Bug 26296: (follow-up) Make sure title remains mandatory

Bug 26296: (follow-up) Make sure title remains mandatory

This patch adds a flag to the OPAC preferences file marking suggestion
title as mandatory OPACSuggestionMandatoryFields and excluded from
OPACSuggestionUnwantedFields.

The patch also modifies the markup around required fields in the OPAC
suggestion form to comply with changes made in Bug 27668 to mandatory
field styling.

To test, apply the patch and restart services.

- Test the OPACSuggestionMandatoryFields preference. In the modal,
  "title" should be checked and the label in red. It should not be
  possible to uncheck the checkbox.
  - Test that the "Select all" and "Clear all" links don't affect the
    "title" checkbox.
  - Confirm that your selections are still saved correctly.
- Test the OPACSuggestionUnwantedFields preference. In the modal,
  "title" should be unchecked and disabled.
  - Test that the "Select all" and "Clear all" links don't affect the
    "title" checkbox.
  - Confirm that your selections are saved correctly.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>