Bug 18656 - Require confirmation of deletion of files from patron record

Bug 18656 - Require confirmation of deletion of files from patron record

This patch adds a JavaScript confirm to the deletion of files. It also
styles the file deletion link as a Bootstrap button.

To test, apply the patch and open the "Files" page for a patron who has
files attached.

- Verify that clicking any "delete" link prompts for a confirmation.
- Verify that confirming the dialog triggers the deletion of the correct
  file.
- Verify that canceling the confirmation dialog aborts the deletion.
- Confirm that the "Delete" button looks correct.

Signed-off-by: David Roberts <david.roberts@ptfs-europe.com>
Revision for QA: Replaced '.click(function' with '.on("click",function'

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>