Autosave and Autorun options should persist between sessions

[hallpell]

Currently, Autosave and Autorun both default to on each time the page is loaded. Ideally, changing these should change the user preference and remain between sessions (and possibly update upon log in). We currently save the editor theme on a per-user basis, so this should be possible. I haven't looked into how we do the theme, so am unsure exactly how difficult this will be.

A minor quibble I have with this is that we generally always want both of these on by default, and if a student opts out of these features (possibly accidentally, possibly out of curiosity) we'd rather not have that stick until an instructor notices. I think this is less important than giving the user more control over their sessions, but it's worth considering and gives me pause.