Adressverwaltung allow below admin

Allow "Adressverwaltung" of one Pfadi's group to manage the children of this group: Pfadi and Gremium.
Actualy, if a "Adressverwaltung" created a sub-group (Pfadi or Gremium) he can not manage it unless he added himself as admistrateur of this child-group. 
Same modification as to be done for woelfe.rb, pio.rb, biber.rb and for "stufe?" level