Initialize traffic credit of imported users to maximum value
Initialize traffic credit of imported users to maximum value

Closes #196
lukasjuhrich/pycroft,agdsn/pycroft,lukasjuhrich/pycroft,agdsn/pycroft,agdsn/pycroft,agdsn/pycroft,lukasjuhrich/pycroft,lukasjuhrich/pycroft,agdsn/pycroft