Bug 35198: Sort database column names alphabetically on automatic item modification...

Bug 35198: Sort database column names alphabetically on automatic item modification page

This patch modifies the automatic item modification by age page so that
the rule entry form sorts <select>s alphabetically, making it easier to
find the entry you need.

The [% FOR field IN... %] directives now include the "sort" method, e.g.

    [% FOR field IN agefields.sort %]

To test, apply the patch and go to Cataloging -> Item modifications by
age

- Click the "Add rules" button, then the "Add rule" button.
- Check the "Age field," "Conditions," and "Substitutions" dropdowns to
  confirm that the choices are listed alphabetically.
- Fill in the form and save the rule.
- Go back and edit the rule you created. Check that the dropdowns are
  still correct.

Signed-off-by: Andrew Auld <andrew.auld@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit fd258280482e0c84bf6baf61d7054b1c628e53f7)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>