* Activate restricted_data_cache on inmemory cache
* Use ElementCache in rest-api get requests
* Get requests on the restapi return 404 when the user has no permission
* Added async function for has_perm and in_some_groups
* changed Cachable.get_restricted_data to be an ansync function
* rewrote required_user_system
* changed default implementation of access_permission.check_permission to
check a given permission or check if anonymous is enabled
These are
- agenda item speakers,
- motion submitters and supporters,
- assignment candidates,
- mediafile uploader and
- chat message users
but only if the user has respective permissions. Fixed#3002.
