Resolve "Connect scripts to AuTA"

What does this MR do (summary)?

Closes #5 (closed)

Screenshots

What changes have you made (detailed)?

• Now, when the user sets the assignment id from AuTA as the 'approve script' for an assignment, every submission for that assignment will be sent to AuTA, to be checked.
• Script grades can be overriden by edition staff. The final grade for an assignment is now the highest non-script grade of the latest submission or the highest grade of the latest submission if there are only script grades.

Does this MR meet the acceptance criteria?

• The main application was run to make sure the server still runs without errors.
• Tests were written to verify the behaviour of this code.
• Javadoc and other comments were added to make the code understandable.
• The code adheres to the style guidelines.