[Feature request] Add statistics to devices

[jjtbsomhorst]

It would be nice if you could add capabilities measurement_tx and measurement_rx to the devices such thath I can see them in the app.

I tried to add them myself but I got a 'invalid_capability' error during testing. if you want I can give you my repo?

[jjtbsomhorst]

Already added it. Gonna send a pull request