Data Layer updates a "last edit date" field on the Item

Created by: martinburchell

Created by: aliceh75

I think it would be good to have a test that ensures that modifying one item does not update the last modified time on another item.

This would also ensure that the time mocking thing is functioning - at the moment, all the tests check for a single update, so if num_updates was broken and always returned 1 all the tests would still pass.

Created by: martinburchell

Good idea - added

num_updates was returning values other than 1 during development, before I put the action checks in the signal handler.