Initial bluetooth support

Some initial bt support. I have another branch that uses libgnome-bluetooth to get more informaton on connected devices but that needs more investigation since i've seen ui stalls. Next steps would be soft (un)blocking on button press.

I was undecided if we want to show the BT icon in the bar/lockscreen when soft-blocked since the BT icon seem different in that regard. We need to clear that up for wwan/wifi/bt -

Closes: #220 (closed)