Store and allow instructor download of submitted notebook

[labarba]

It's amazing how many times students insist that the grader made a mistake and gave them an incorrect score! If an assignment has a deadline, they might send a notebook (by email attachment) after the deadline and insist this is their submitted work, but the grader made a mistake. The instructor is left trying to explain to the student that no, the grader does not make mistakes, and the notebook you've sent me must be different from the one you submitted. SIGH.

So, we need the grader to keep a copy of the (last) submitted student notebook, and allow downloading it, so when a student comes arguing about their score we can have evidence at hand.

It would also be useful to have a time stamp of the (last) submission. I know you can see a time stamp by going into staff debug mode, and maybe that's just what to do. But maybe it can be displayed to the student in the component.