feature idea - Discrepancies tab - list scans with no quality rating

[jcf2]

Addition to the Discrepancies tab: once scans that are in the imaging list but not in the quality list are given a default/na value in the latter, it would be good to list them under Discrepancies as "Scans with no quality rating" (as suggested on #39).

Here are some ideas for listing that come to mind:

1. For a scan session that has no quality rating for any scans: if feasible, it would be nice not to list all the individual scans, but instead just list the scan session (could be a separate list)
2. For any missing ratings that are for scans not marked "Overdue", it would be nice to see that (this could be via just including the Overdue column; or, maybe a separation into overdue/not overdue lists?)