Studious

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Several added features in this update, including:
* Option to show a sticky notification for the current and next class
* Backup and restore timetables to external or cloud storage
* Export timetable as .png image
* (optional) Map fragment returns
* Refreshed exams and homework screen

As well as:
* fixed a crash on the homework and exams screens for kitkat and below
* fixed reminders leading to the wrong screen
* performance and bug fixes