Bug 37612: Batch patron modification should accept both cud-show and show ops

Bug 37612: Batch patron modification should accept both cud-show and show ops

Just like with batch item modification, batch patron modification can accept
either a POST of a lot of data, which might be more than Apache's default
URL length limit, or a GET of a little data. Or at least it could, if both
the op 'cud-show' and the op 'show' were accepted. Show isn't doing any
creation or updating or deleting, it just has to be cud-show because it needs
to be able to accept large POSTs. So when it is only getting a little data, it
should be willing to take a GET with op=show just like batch item
modification does.

Test plan:
1. Without the patch, Tools - Patron lists - New patron list - give it a
   name and Save
2. Type enough characters in the Patron search input to find a patron (I
   like ace for poor often-used Henry Acevedo) and click on a patron in
   the list of results
3. Click Add patrons
4. Click Patron lists, and in the Actions menu for your list, choose
   Batch edit patrons. Note that the page that loads doesn't show any patrons
   or UI to edit them, only a message about "No patron card numbers or
   borrowernumbers given."
5. Apply patch, restart_all
6. Repeat step 4, but this time get a page with your patron listed, and a
   form to change things about the patron record.

Sponsored-by: Chetco Community Public Library
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>