Avoid updating data in older courses that haven't been accessed in awhile

[jonespm]

Thank you for contributing to this project!

Describe your problem or feature you'd like added

Related a bit to #1327 and #827 it would be more efficient to only process course that have been accessed within the last X days.

Describe the solution you'd like

I think this might require adding a column to the courses table that will update something like a date_last_access whenever anyone goes to that course. And then in the verify_course_ids just doesn't process these courses if they haven't been accessed in X days. We could also rely on the eventlog_log table but the courses there are in JSON so would take a little more processing.

This probably isn't a high priority now but something we've talked about as more classes get added.

[jennlove-um]

Add the date last accessed as a first step to getting this done.