Bug 38275: Fix patron card creator image delete

Bug 38275: Fix patron card creator image delete

This change changes the patron card creator image delete from a
GET to a POST, and supports single delete and multi-delete.

Test plan:
1. Apply the patch (and refresh browser JS cache)
2. Go to http://localhost:8081/cgi-bin/koha/patroncards/image-manage.pl
3. Upload multiple images
4. Select all the images using the checkboxes
5. Delete one image using the "Delete" button in the row
6. Note that only the image selected using the "Delete" button is
deleted and the other images are de-selected
7. Delete multiple images using the "Delete selected" button
8. Note that the correct images are noted in the confirm message,
and the correct images are deleted

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>