News: Reworking timetables, subjects and grades

[rine77]

Hello together,
I started reworking

• timetables (switched from get_my_timetable to get_timetable) -> to be added as a HA calendar
• subjects (all subjects of your school are being fetched now, you choose which are needed)
• grades (try to attach them to the subjects sensors in a better way than just adding attributes)
• polishing code and make it more readable

gimme some time!
/rine