* change get_restricted_data and get_projector_data to always use a list
* Add typings to all get_restricted_data and get_projector_data methods
* Replace CollectionElementList with a real list
* Fixed arguments of inform_deleted_data
* Moved CollectionElementCache to cache.py and refactored it
* Run tests with cache enabled (using fakeredis)
* Add caching support to users/group
* Add a function has_perm that works with the cache.
* Removed our session backend so other session backends (without the database) can be used
* seperate unittests and integration tests
* moved old tests in seperat folder 'old'
* created a testrunner that does not create a testdatabase, if only unittests are run
* wrote some unit- and integration tests as examples
* fixed user.get_short_name() to use the sort order from config
* fixed wrong url_pattern in the user app