lower class names for classes in /etc/sophomorix/users/class.map

[zefanja]

If you have a mapping with a capitalized first letter (like 12;Klasse12) in /etc/sophomorix/users/class.map the unix group is not created which causes serveral problems (e.g. not being able to add classes to p_wifi, because the group id is not found (because it does not exist)).

Idea: Lower the names in class.map by default (like in schueler.txt AFAIK).