Create / delete person and group

Provide way to create and delete persons and groups in frontend

Important: We should NOT hard delete persons and group. We should soft delete them with django-reversion.

added part::frontend prio::2 type::feature labels

assigned to @debdolph

created merge request !265 (merged) to address this issue

mentioned in merge request !265 (merged)

mentioned in commit 8c68379e

mentioned in commit 7ba87e5a

closed via commit 8c68379e

closed via merge request !265 (merged)