Acq: Delete line items marked "cancelled/deleted" from an activated PO

I looked at this while looking at https://bugs.launchpad.net/evergreen/+bug/1115599 to see if I could fix it at the same time. Unfortunately, the logic is a little different here. The "Delete Selected Items" menu option is only enabled for picklists, pending purchase orders, general search, and the view/place order interfaces. It becomes disabled for activated purchase orders.

 Since PO's continue to be activated purchase orders even after lineitems are cancelled, the option is disabled for those lineitems. However, we don't want to allow the menu item to enabled for all active orders because we don't want staff deleting items with an on-order status. Ultimately, I think we need a way to allow it for cancelled items and not for on-order items.

I agree with Kathy, if we want to be able to delete line items after a purchase order is activated we want to make sure it is only for cancelled items.

It would also be helpful if some record of the line item remained in the database after the deletion (like with items that are deleted from the catalogue) so that staff could track what had hapened in the event of a line item being deleted accidently. Right now, as far as I'm aware, if you delete a line item from a selection or pending purchase order the line item is completely gone and there is no way to track what happened.

Retaining a record of a deleted line item might be useful, especially if the line item were deleted by mistake and there is a need to reinstate it.

Regarding tracking deleted line items, they do end up in the auditor table acq.acq_lineitem_history, which could if need be be supplemented by adding more auditor tables (e.g., on acq.lineitem_detail). There's at present no UI for accessing them, however.