Automatic feedback selection, config cleanup

[malthee]

• Implemented automatic and random feedback selection based on feedbacks received. Students who have received less feedbacks on submissions and reviews are more likely to be selected.
• Added save mechanism to CSV for the count of feedbacks a student has received.
• Integrated save-feedback command as prompt into mail command.
• Moved the prompt of some properties into the ConfigHandler and added backing fields to avoid code duplication.
• Renewed readme.md with new functionality, better readability and tutorial for shared tutor work.
• Name of Moodle authorization cookie can now be set through the ConfigHandler.

[malthee]

Not ready for merge yet, fixing tests

[malthee]

Tried executing pipeline locally but it succeeded, don't know whats wrong here

[malthee]

Ready to merge, fixed the test bug by excluding the java.nio.file.Files library, which caused an UnsatisfiedLinkError because the classloader has already loaded an instance of it.