Bug 11795 - Use validation plugin when creating new Z39.50 server

Bug 11795 - Use validation plugin when creating new Z39.50 server

The page for adding a new Z39.50 server includes some custom form
validation JavaScript which can be removed in favor of HTML5 validation
attributes and Koha's built-in validation plugin. This patch does so.

To test, apply the patch and go to Administration -> Z39.50 client
targets -> New Z39.50 server. Try submitting the form with any of the
following error conditions:

- Missing Z39.50 server name
- Missing hostname
- Missing port
- Non-numeric port
- Missing database
- Non-numeric rank
- Non-numeric timeout

These errors should trigger a validation warning.

Submission of the form with valid data should work correctly. Editing
an existing Z39.50 server should also work correctly.

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Amended patch: replace tabs with spaces

Signed-off-by: Galen Charlton <gmc@esilibrary.com>