Bug 11806 - Use validation plugin when creating new OAI set

Bug 11806 - Use validation plugin when creating new OAI set

The form for adding a new OAI indicates that two fields are
required but does nothing to enforce this rule. This can be
handled client-side with HTML5 validation attributes and Koha's built-in
validation plugin. This patch implements this.

To test, apply the patch and go to Administration -> OAI sets
configuration -> New set. Try submitting the form without entering a
setSpec and/or setName. Doing so should trigger a validation warning.

Submission of the form with valid data should work correctly. Editing an
existing set should also work correctly.

Followed test plan. Patch behaves as expected.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Passes all tests and QA script, works as described.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit e634a5ad82e9fa0aef96ae5a23bb5b389d1704e7)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>