NetworkStatus: ignore invalid and unsupported connection types

Some connection types (like wimax) are not supported by the menu, and
should be ignored instead of throwing exceptions. Also, NetworkManager
had a bug that sent connections with invalid settings. This should not
happen, but in case it does, we will not blow up, but just log a warning
and continue silently.

https://bugzilla.gnome.org/show_bug.cgi?id=646355