update details html

optimizations for timetables

display five individual timetables for every day instead of one timetable for every day on mobile devices

Merge branches 'dev' and 'pwa-optimized' of https://github.com/Katharineum/school-apps into pwa-optimized

Some small but important changes

# Conflicts:
#	.idea/misc.xml
#	.idea/school-apps.iml

merge into dev

Show missing teachers (absences) in the header PDF