Various changes and fixes
- More Star Tracker updates. PR #762
- AirspyHF: added decimation by 128 and 256. PR #764
- SSB demod: use log (dB) for volume setting
- CW keyer: revised the WPM calculation
- SoapySDR: a few fixes. PR #766
- RTLSDR: changed BW setting limits. PR #766
- Various changes in build and compiler warning fixes. PR #766
- NFM demod: cosmetic changes. PR #766
- Removed FPS limitation in WSSpectrum. Implements #767