Receive Antenna Switching Client

- Websockets to connect to server application
- JSON data
- Generate Equidistant Azimuthal projection center on lat,long (Maidenhead grid)
- Map is zoomable
- Source map is 2:1 aspect Equirectangular (Plate Carree) projection
- Maps and night shading rendered in separate thread to avoid GUI blocking
- Nighttime shading of map (greyline), updated in 5-min intervals
- User selection of: band (in manual mode), group, antenna
- Display modes: compass (with map) or List (buttons)
- Features: scanning (w/ user defined delay), tracking, lock, swap antennas,
  disabled scan (per antenna)
- PTT (TX/RX) state indicator
- separate UI files for desktop vs. small touchscreen (ie. Pi)
- tested in Linux and Windows (mingw32 / GCC 8)