Morse decoder feature

[f4exb]

Implemented as a feature so that it can use the audio of not just one type of Rx channel. More specifically and as an initial list: AM demod, NFM demod, SSB demod and WFM demod. It can pick up the audio just as the Demod Analyzer does.

The GGMorse library seems convenient to handle the decoding part: https://github.com/ggerganov/ggmorse. However the CMake file as written now does not install the header so we may use my own fork instead.

This GGMorse library is also implemented as an Android app or web application and it seems to give good results as good as FLDigi which is the usual reference.