Silence logging while detecting devices

@kentquirk Do you mind taking a look at this? It was getting a bit painful to debug things with the continuous scanning, so tried to do something about the logging. It feels a bit of a hack, but it's the best I could come up with right now. Feel free to share any other suggestions :)

Btw, related to this, I also added on `mvp` the possibility to stop the scanning from the JavaScript console:

```
> app.refs.scan.stopScanning();
> app.refs.scan.startScanning();
```