Merge remote-tracking branch 'origin/feature/timetable-hints' into feature/timetable-hints

# Conflicts:
#	.idea/misc.xml
#	.idea/school-apps.iml
#	README.md
#	schoolapps/schoolapps/urls.py
#	schoolapps/static/common/helper.js
#	schoolapps/timetable/templates/timetable/substitution.html