Bug 17672: Add damaged_on to items and deleteditems tables

Bug 17672: Add damaged_on to items and deleteditems tables

This patchset adds a 'damaged_on' column to store the date an item is
marked damaged, analogous to withdrawn_on and itemlost_on

To test:
1 - Apply patch
2 - Mark an item damaged via moredetail.pl (Items tab on left in
        details)
3 - Note the damaged on date apears below
4 - Unmark the item, the date is removed
5 - Go to the edit items screen (from top bar 'Edit->edit items')
6 - Mark item damaged - check db or moredetails.pl to see damaged_on
date
7 - Unmark item damaged - confirm date is removed
8 - prove t/db_dependent/Items.t

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Charles Farmer <charles.farmer@inLibro.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>