Set the state of the wireless enable checkbox correctly on startup and on state change.
The switch controls the NM daemon's soft wireless enable but reflects the state of that and of any system hardware rf kill switch.

Act on UI events and daemon state changes in this area at the appropriate levels: The interface items listen to the daemon, the wireless items set their wireless specific UIs, and react to daemon changes whereever possible resulting from UI events instead of the daemon and the UI.

Rename InterfaceGroup::enableInterface() to enableInterfaces() as it may affects more than one.