Use new icon set everywhere

aleksis/apps/alsijil/menus.py

.../alsijil/templates/alsijil/absences/register_confirm.html

...apps/alsijil/templates/alsijil/class_register/groups.html

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

...apps/alsijil/templates/alsijil/class_register/person.html

...pps/alsijil/templates/alsijil/class_register/persons.html

...sijil/templates/alsijil/class_register/students_list.html

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

aleksis/apps/alsijil/templates/alsijil/excuse_type/list.html

...s/apps/alsijil/templates/alsijil/excuse_type/warning.html

aleksis/apps/alsijil/templates/alsijil/extra_mark/list.html

...sis/apps/alsijil/templates/alsijil/group_role/assign.html

...s/alsijil/templates/alsijil/group_role/assigned_list.html

aleksis/apps/alsijil/templates/alsijil/group_role/list.html

...templates/alsijil/group_role/partials/assigned_roles.html

...lates/alsijil/group_role/partials/assignment_options.html

...is/apps/alsijil/templates/alsijil/group_role/warning.html

...ps/alsijil/templates/alsijil/partials/lesson/heading.html

.../alsijil/templates/alsijil/partials/lesson/prev_next.html

...alsijil/templates/alsijil/partials/lesson/tabs/notes.html