Bug 12648: Link patrons to an order

Bug 12648: Link patrons to an order

This patch is the main patch.

This feature adds the ability to link patrons to an order.
On that way, they will be notified when the order is completely
received.

Test plan:
1/ Execute the updatedb entry and verify you have a new notification template in your table (tools/letter.pl).
code: ACQ_NOTIF_ON_RECEIV, module: acquisition
2/ You can edit it if you want
3/ Create a basket and create an order with 1 or more items
4/ Link 1+ patrons to this order
5/ Close the basket and receive the order
6/ When you have received all items for this order, all patrons attached
will be notified. Check the message_queue table to check if the letters
have correctly been added to the queue.

Signed-off-by: Paola Rossi <paola.rossi@cineca.it>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>