Bug 19383: Add ability to print hold receipts automatically

Bug 19383: Add ability to print hold receipts automatically

Some libraries don't wish to require librarians to confirm each hold during checkin. Instead they would like to only be alerted that a hold was filled.

Test Plan:
1) Apply this patch
2) Run updatedatabase.pl
3) Enable the new syspref HoldsAutoFill
4) Check in an item that should be trapped for a hold
5) Note that instead of the modal asking if the hold should be filled,
   instead you get a message box showing the hold was filled, along
   with a button to print the hold slip.
6) Enable the new syspref HoldsAutoFillPrintSlip
7) Repeat step 4
8) Note the same behavior, but this time the print dialog displays
   automatically

Signed-off-by: Séverine QUEUNE <severine.queune@bulac.fr>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>