Last saved state does not account for blocks & files changing

[ml-evs]

We need to update last_modified on an item when a file or block that is attached to it is added/updated/saved, otherwise the UI is misleading and seems to say that the block has not been saved.

Since the item data does not get redownloaded between the calls, we probably also need to manually set this in the UI at some point, though this could also give false security since the item may not have been saved successfully.