Implement shuffled next ungraded
Closes #257 (closed)
This is basically a minimal implementation of what was done in !116 (closed), which is 800 commits behind master. It was easier for me to reimplement than to merge. Also replaces !187 (closed), which would randomly select from server, because we decided against that.
Both !116 (closed) and !187 (closed) should be closed if this is merged
Edited by Otto Kaaij