Optimize lesson overview for mobile and tablet devices

aleksis/apps/alsijil/static/css/alsijil/lesson.css

aleksis/apps/alsijil/tables.py

...apps/alsijil/templates/alsijil/class_register/lesson.html

...s/alsijil/templates/alsijil/class_register/week_view.html

.../alsijil/templates/alsijil/partials/lesson_prev_next.html

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

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