Re-added comments to be able to transfer them.
Added maintenance scripts for data migration.
small bugfix
Added a grading guide for assignments.
Merge remote-tracking branch 'github/production'
Merge remote-tracking branch 'github/mshavlov'
Better distinction between comments and feedback, and submission feedback improved.
Improved a bit the interface.
Create README.md
Added maintenance script.
Merge remote-tracking branch 'origin/master' into production
Fixed bug: representation does not work for None