Add CC property

Fix the result dialog not appearing problem. Fix some schema issues.

Make marking window modal. Fix bugs with incomplete results.

Change 'special' criterion to text fields. ...

* Allows arbitrary values for things like late penalties (within specified ranges).
* Can abuse this to mark exams.

Switch DAO to using submission_id for finding students. Recursive code reformat.

Minor cleanup. Library updates. Update schema to latest version.

Bunch of stuff that I forgot to commit a year ago. Whoopsy.

Converted to Gradle project, and switched to FlatLAF.