Remove thesis track and fix imports

[niclasheun]

Description

This is a cleanup PR, which removes the Thesis Track completely from this project, as ThesisTrack has its own repo and every thesis related URL request is already redirected.

Type of change

• [x] Bug fix (updating dependencies)
• I updated a version of jgit in the gradle config file, so that it starts up without issues
• [x] Cleanup
• Removed all Thesis Track related components and controllers on client and server side
• wrote a database migration to delete the thesis track related tables from the database

How Has This Been Tested?

I tested the database migration on my local machine. Further, I made sure to only remove dead code, and to really remove everything which is solely Thesis Track related

CAREFUL: This PR includes a database migration, which will delete all Thesis related database tables from the prompt database. Please review first, if this database migration is wanted/correct and if the data in these database tables is not needed any more.

[Mtze]

Thanks for the change - I'd like to postpone the merge of this until after the intro course since this is a pretty hefty change :)