add a "custom" sdr option

[n0p]

so we can specify the options to soapySDR like "driver=uhd,addr=192.168.1.12"

[BatchDrake]

You can already do that:

• Go to profile settings, select SDR and any device (Dummy is fine)
• Open device specific tweaks
• Change the driver to uhd and/or other parameters
• Click OK and start the SDR

Of course this assumes that uhd is something supported by your current SoapySDR installation, otherwise it will fail.