Bug 12937: Deleting suggestions should ask for a confirmation

Bug 12937: Deleting suggestions should ask for a confirmation

On the suggestion management page, the librarian can choose to delete
suggestions but no confirmation is needed.
This could produce unexpected lost of data.

Test plan:
- go on the suggestion management page
- don't select any suggestion and try to delete (check the checkbox and submit the form).
  Verify that you get an alert.
- select 1 suggestion and delete it, verify you get a confirmation
  message
- select 1+ suggestions and delete it, verify you get a confirmation
  message

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>