Support stream args in GrOsmoSDR

[guruofquality]

This is more of an issue for the soapy support in GrOsmoSDR, which is a different but related project. Its just easier to track it here. The GrOsmoSDR API doesn't support stream args, but many of the support modules make use of them.

The simple work around is to stash the device args provided by the user and pass them into setupStream() -- that way GrOsmoSDR users can get full use of the stream arguments through the existing API and any GrOsmoSDR command line tools that only take the device args.