Support multiple devices of the same type

[larsks]

I have two RTL-SDR dongles attached to my system. They have different serial numbers, so that it's possible to tell which is which...except that PLSDR doesn't surface this information, nor does it provide any means of specifying which device is in use, which leads to two problems:

1. I can't select the device I want to use, and
2. I can't even tell which device PLSDR is using.

GQRX presents the devices like this:

And CubicSDR does it like this:

GQRX also allows one to specify a device manually by setting the RTL device number (e.g, rtl=0 or rtl=1). Possibly one of these options would work for PLSDR?