Add rtlsdr selection option

[murrayma]

The RTLSDR device index isn't reliable for configurations with multiple RTL SDR's. RTL-SDR's can be programmed with a user supplied serial number. This patch allows configuring the RTLSDR by device serial number matching instead of device index. This should solve #22 as well.

[dseven]

Thanks for doing this. It saves me some effort 👍

It might be nice if it could log something to the effect of 'unable to find device with serial matching "XXX"' - as it is, it ends up just logging "Unable to open device", which is a bit misleading. For bonus points, it could log all (non-matching) devices found in that case too.

P.S. I should note that I'm just another user, with the same need (to be able to specify a device by serial)

[murrayma]

Thanks for doing this. It saves me some effort 👍

It might be nice if it could log something to the effect of 'unable to find device with serial matching "XXX"' - as it is, it ends up just logging "Unable to open device", which is a bit misleading. For bonus points, it could log all (non-matching) devices found in that case too.

P.S. I should note that I'm just another user, with the same need (to be able to specify a device by serial)

Good idea! Thank you.