Only export submission summary

[pdawyndt]

Context: The submission summary is a CSV-file containing information about the students, the exercises and the submissions. When exporting submissions for a course or a series, it is possible to also export this CSV-file (it is included in the .zip folder).

Issue: This file has value on its own, however, it is not possible to export it without also exporting the submissions themselves. This is quite time consuming, especially since it comes with a lot of into (the submitted solutions itself) that is not needed if you also need the metadata.

Suggested solution: Provide the option to only download the submission summary, either as a separate action in the course/series menu, or as an extra option/button in the export process.