Bluetooth: fix ngettext call

https://bugzilla.gnome.org/show_bug.cgi?id=709043
NetworkMenu/NMDeviceWireless: use the device state instead of active connection state

Since we connect to signals for that, we need to sync on that, or
we can miss a notification.

https://bugzilla.gnome.org/show_bug.cgi?id=709043
NetworkMenu/NMConnectionDevice: grab the connection before using it

If the active connection for the device is not the primary or
activating globally, it won't have the _connection and _primaryDevice
expando properties, so grab them from the settings object.

https://bugzilla.gnome.org/show_bug.cgi?id=709043