Bug 16004: Replace items.new with items.new_status

 Bug 16004: Replace items.new with items.new_status

The items.new column is badly named, the Koha::Item->new accessor will
never returns this value, but the constructor will be called instead.
This patch renames it with new_status to avoid the ambiguity.

Test plan:
0/ Do not apply this patch
1/ Define some rules in the "Automatic item modifications by age" tool
with at least one items.new field used
2/ Apply this patch
3/ Execute the update DB entry
4/ Reload the tool page and confirm that the changes have been taken
into account

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>