Query can send no school-term and will receive the result for the
current school-term. With the additional school-term parameter the
frontend now knows which school-term is current.

Not shure if they should be kept insided the main
StatisticsForPersonCard or pushed into the subcomponents.

Previously there was a statistics undefined error while apollo was
still loading.

person & schoolTerm are both objects now in personOverviewCardMixin.

Using count wrapper types to avoid duplicating the counted types.

& use in DocumentationBatchCreateOrUpdateMutation & AbsencesBatchCreateMutation.

& share between query & mutation.

& use documentations instead of lesson-events

into get_documentations_for_events
& get_for_coursebook
This makes it reusable for further purposes (absences).