Feature idea: Timing metrics of how long it took to perform a scan

[jonespm]

I think it would be useful to capture when a scan started and when it completed. Ideally each individual part would be timed for future performance improvements but generally it would be nice to know just the overall scan duration for larger courses that might try to do a rescan or for future load estimations for admins.

This should be exposed both in the UDOIT admin in the Courses page and possibly also instructor views.

The column "Last Scanned" is currently available. It looks like this is captured and represents the time when "Last Scan Completed". I think displaying the hour and minute as well as capturing at the start of this as "Last Scan Started" it would probably be enough to do the calculation.