Make lessons with event pruple

Include events + hints

Feature/faq

- Arrange print icon right
- Add line break for header information in LaTeX
- Show one-hour absences with only one number (e.g. 1.) instead of two (e. g. 1.-1.)
- Add dots to lesson numbers in absences

# Conflicts:
#	schoolapps/timetable/templates/timetable/substitution.html

remove kanboard in readme.md

Improve REBUS

REBUS:
- Repair form validation (Remove required attributes, issue #166)
- Remove Kanboard settings (issue #206)
- Resort categories (issue #176)
- Show all rooms by presentation device issues (issue #204)
- Add toast if form isn't valid