Administration option : Levels of domain conceal

[norrs]

A level in campaign settings of how many levels ("." == dots) should not be concealed by this method: https://github.com/dotKom/onlinepetition/blob/master/onlinepetition/petition/models.py#L75

(ie, incase emails are from ansatt.ntnu.no , show xxxxxxxxxxxxxxxx.ntnu.no to show which university the user is from.)