Do not create personal notes for cancelled lesson periods in mark_absent

See merge request !81

Merge branch '99-add-option-to-reset-personal-note-delete-at-students-view-for-class-teachers' into 'master'

Resolve "Add option to reset personal note ("delete") at students view for class teachers"

Closes #99

See merge request !86

Merge remote-tracking branch 'origin/99-add-option-to-reset-personal-note-delete-at-students-view-for-class-teachers' into 99-add-option-to-reset-personal-note-delete-at-students-view-for-class-teachers