Bug 25694: Add ability to delete a Marc Modification Template when viewing

Bug 25694: Add ability to delete a Marc Modification Template when viewing

This patch adds a "delete template" button to the MARC modification
templates "Edit actions" view.

To test, apply the patch and go to Tools -> MARC modification templates.

 - On the main MARC modification templates page the toolbar should have
   only one button: "New template."
 - Click the "Edit actions" button for an existing template.
 - On the "Actions for..." view there should be three buttons, "New
   template," "New action," and "Delete template."
   - Test that the "Delete template" button works correctly.

Signed-off-by: Kelly McElligott <kelly@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>