Ability to override scores for a folder / course?

[cmcfadden]

This comes up in a lot of different ways - a student misses one response in a folder, or missed a class entirely for an excused reason, etc. Right now, we can either insert a fake response in the responses table, or the instructor can update the canvas gradebook (assuming it's a case where we won't overwrite those scores with a fresh sync).

Maybe it's time to consider some sort of override placeholder for this. There are a bunch of cases to account for given the different grade modes, so we'd need to do some brainstorming both on UI and data structures.