Bug 15534 - Add the ability to prevent a patron from placing a hold on a record with...

Bug 15534 - Add the ability to prevent a patron from placing a hold on a record with available items

Some libraries would like to prevent patrons from placing holds on
items where there are other items available for the patron to
check out.

Test Plan:
1) Apply this patch
2) Browse to the circulation rules
3) Note the new option for "On shelf holds allowed"
4) Set the rule to "If all unavailable", set "item level holds" to allow
5) Find a patron/branch/itemtype applicable to this rule
6) Ensure at least one item on the record is available for the
   patron to check out
7) Attempt to place a hold for the item
8) Note you cannot place the hold
9) Check the available item out to another patron
10) Note you can now place a hold for the first patron

Signed-off-by: Andreas Hedström Mace <andreas.hedstrom.mace@sub.su.se>
Works as intended!

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>