Bug 20815: Add ability to choose if lost fee is refunded based on length of time...

Bug 20815: Add ability to choose if lost fee is refunded based on length of time item has been lost

This adds the ability to not refund lost item fees on return if the item
has been lost for more than a given number of days.

Test Plan:
1) Set the new system preference NoRefundOnLostReturnedItemsAge to a number of days
2) Find a lost item that has been lost longer than that NoRefundOnLostReturnedItemsAge days which would have otherwise been refunded
3) Return the item
4) Note no refund on the lost item fee was processed, the fee remains unchanged
5) prove t/db_dependent/Circulation.t

Signed-off-by: Deb Stephenson <DStephen@dubuque.lib.ia.us>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>