Bug 11766 - Use validation plugin when creating new authority type

Bug 11766 - Use validation plugin when creating new authority type

The new authority type entry form uses custom form validation
JavaScript. This patch removes it in favor of using HTML5 validation
attributes and Koha's built-in validation plugin.

To test, go to Administration -> Authority types and click "New
authority type." Try submitting the form without entering any data. You
should see a warning about required fields. Upon entering text in those
fields the warning should disappear.

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit ac9d872fefc867d4f068d425bcfcb929435809bd)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>