Code review fixes

Fix several problems in the code review MR

Serverside:

Remove submission flagging in async scheduler as it is not implemented well:

• it is written in the assignmentprogressions folder where it doesnt belong
• it breaks assignment progression
• it goes over all submissions in the whole system
• it is not needed as it is already triggered once a submission is made

Recreated migration scripts

Add extra validation for code annotations and submissions

Remove default values for certain columns

Weblab import is commented out as it doesnt work well yet:

• users who are not in the database are simply skipped now
• they cannot be automatically added as we use netid's are identifiers, not student numbers
• in the current implementation a Multer object is passed instead of a raw string, which causes it not to work in production
• the import doesnt work when a assignment has multiple versions

Clientside:

• I did not have much time for the client side
• I quickly went through the code and tried things out manually
• Seems to work ok afaik