Bug 37489: Separate forms for uploading and deleting a patron image

Bug 37489: Separate forms for uploading and deleting a patron image

This patch creats a new form for image deletion that is submitted via the 'Delete' button on the modal.

To test:
1) Turon on the 'patronimages' sys pref
2) Visit a patron page, you should see an image module on the left.
3) Click on the image to edit it. Upload a new image.
4) Edit the image again, press delete and confirm the popup.
5) Note that it will not let you delete because of the required file.
6) Apply patch
7) Attempt to delete again, this time it is successful.

Signed-off-by: Roman Dolny <roman.dolny@jezuici.pl>
Signed-off-by: David Cook <dcook@prosentient.com.au>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>