Assessment Summary report #1595 (replaces problemset summary report)

@sefk  please.

As it turns out, this was quite simple as it is a report of a single assessment with same format as the Combined Summary Assessments report.

Also, includes a small fix to display the field_name if the human_name is not available; applied to previous assessment reports.

Also, includes some final cleanup of the old problem set reports that are no longer required.