Bug 10748: Add the ability to block return of lost items

Bug 10748: Add the ability to block return of lost items

Mimicking what does BlockReturnOfWithdrawnItems we can easily add a new
syspref to block return of lost items.
This patch adds BlockReturnOfLostItems, if set to 'Block' a item marked
as lost cannot be checked in.

Test plan:
1/ Set BlockReturnOfLostItems to 'Do not block'
2/ Check an item out to a patron
3/ Edit the item and mark it as lost (*)
4/ Check the item in
=> The item is checked in
5/ Edit the item and remove the lost status
6/ Check the item out again
7/ Edit the item and mark it as lost (*)
8/ Check the item in
=> The item is not checked in

(*) There are 2 ways to mark an item lost:
- From the item list view (/catalogue/moredetail.pl?biblionumber=42)
If you set the lost status from this form, the issue will be returned
Maybe this should be optional (?)

- From the edit items form (/cataloguing/additem.pl?biblionumber=42)
It is the form you must use to not mark the issue returned.

Sponsored-by: BULAC - http://www.bulac.fr/
Signed-off-by: Dominic Pichette <dominic@inlibro.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>