Some reorganization
Soapy SDR support becomes an option triggered by --soapy on the command line. This implements #718
The original VOR demodulator is replaced by the "single channel" version and the VOR localizer feature. This is to keep only the version that conforms to the general design of one channel one flow ensuring real multi tasking. Also the usage is more flexible possibly with just one channel that is used for more than one VOR in time sharing. Also more than one receiver can be used which could be more efficient if VORs are far apart in frequency, This implements #1223 The original code is kept for reference as the "multi channel" VOR but is not part of the build.