Add a simple way of extracting the list of submissions.

[oseppala]

Currently there is a view for extracting completed reviews, but it is not possible to extract a table of submissions along with their review statuses. Tracking who has not yet submitted work and who has not began to review etc. becomes complicated. Extracting the html from the submission list is problematic as there are merged table cells that make importing to excel etc hard. A simple CSV would suffice.

[khanetor]

/exercises/183

[khanetor]

make a button to download csv