Add Pycroft privileges for membership and traffic assignments.
Add Pycroft privileges for membership and traffic assignments.

fixes #486

agdsn/pycroft,agdsn/pycroft,lukasjuhrich/pycroft,lukasjuhrich/pycroft,agdsn/pycroft,agdsn/pycroft,lukasjuhrich/pycroft,lukasjuhrich/pycroft,agdsn/pycroft