Merge branch '258-add-export-functionality-to-course-book' into 'master'

CHANGELOG.rst

...pps/alsijil/frontend/components/coursebook/Coursebook.vue

...jil/frontend/components/coursebook/CoursebookControls.vue

.../frontend/components/coursebook/CoursebookPrintDialog.vue

aleksis/apps/alsijil/frontend/index.js

aleksis/apps/alsijil/frontend/messages/de.json

aleksis/apps/alsijil/frontend/messages/en.json

aleksis/apps/alsijil/model_extensions.py

aleksis/apps/alsijil/models.py

aleksis/apps/alsijil/static/css/alsijil/full_register.css

aleksis/apps/alsijil/tasks.py

...sis/apps/alsijil/templates/alsijil/partials/absences.html

aleksis/apps/alsijil/templates/alsijil/partials/legend.html

...pps/alsijil/templates/alsijil/partials/lesson_status.html

...lsijil/templates/alsijil/partials/lesson_status_icon.html

...pps/alsijil/templates/alsijil/partials/objects_table.html

...s/alsijil/templates/alsijil/partials/person_overview.html

...lsijil/templates/alsijil/partials/persons_with_stats.html

...il/templates/alsijil/partials/register_abbreviations.html

...sijil/templates/alsijil/partials/register_coursebook.html