Bug 25184: Add syspref

Bug 25184: Add syspref

It's entirely possible that some libraries are relying on the current
before for part of their workflow. Do to this possibility, it seems like
a good idea to control this behavior via a system preference.

Test Plan:
1) Apply this patch set
2) Run updatedatabase.pl
3) Set TrapHoldsOnOrder to "don't trap"
4) Set an item's notforloan value to -1
5) Place a hold on that item
6) Check in the item
7) Note the item is not trapped for hold
9) Set TrapHoldsOnOrder to "trap"
10) Check in the item
11) Koha should now ask if you'd like to trap the item for the hold!

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>