rework to use groups as main model for consents, implemented control center

src/frontend/src/app/services/api.service.ts

src/frontend/src/environments/environment.prod.ts

src/frontend/src/locale/messages.de.xlf

src/frontend/src/locale/messages.xlf

src/frontend/src/theme.less

...08_verb_remove_providerschema_essential_verbs_and_more.py

src/providers/models.py

src/providers/serializers.py

src/providers/views.py

src/static/provider_schema.schema.json

src/static/provider_schema_h5p_v1.example.json

src/static/provider_schema_moodle_v1.example.json

src/users/models.py

src/users/serializers.py

src/users/urls.py

src/users/views.py

src/xapi/models.py

src/xapi/tests/tests.py

src/xapi/tests/tests_verb_id_validation.py

src/xapi/views.py