Display a updated progress of what's being scanned so user knows something is happening

[jonespm]

In a course with a lot of content UDOIT 3 just displays a static message with a spinner like

If the scan takes awhile, longer than a few minutes because of a lot of content, there's no indication to the user anything is happening and they may be tempted to refresh. This may need some type of communication between the backend process that's running the process and the frontend.

The previous version of UDOIT actually showed a live updated progress of what was being scanned which was nice.

This is somewhat related to #718 and #856