access.ts refactor

[jahndan]

It currently does not support allCourses.json—I'm most likely just going to create a separate variant of the default export with slightly altered methods that can't be misused (getCourse by id does not make sense for this file).

• [x] type definitions and annotations
• [x] restructure of Access methods (typescript makes a lot of stuff redundant)
• [x] mostly finished version of it with the common usage stuff fully working
• [x] general optimisations (no need for clones to be made, maybe manage the redundancy stuff inside the file?)
• [x] access.ts support for allCourses.json
• [x] double check for conflict

[jahndan]

forgot to make an issue for this, but most of it is already done