Task versioning and replay history

[anthonygego]

It would be interesting to store, in some way, task versions in order to know with what version of the files an assessment was made. This could help the teacher find erroneously graded submissions that would need to be replayed. This mecanism should take into account that files can be shared among different instances.

Once this is working, it would be great to keep a replay history and show it to the students so that they can ensure they were all graded with the same file versions for exams, and also make sure no replay was made after grades publishing without their consent. This should be informative for students but not coercitive for teachers as they can replay a submission in favor of the students.