sdr++brown (fork) and client-server remote TX / mobile mode

[sanny...@gmail.com]

Gentlemen, the baseband compression is ready for preview / try in sdr++ brown fork. 

All new features (all optional):

1) lossy baseband compression

2) TX over sdr++ protocol - also compressed to 6ksps 16bit instead of 48000 (not further)

3) password authentication on remote access: "--password abcde". Validated on the start play, not upon connect.

4) buffering on rx/tx

5) new connection to server will drop previous connection if previous connection was idle.

6) can select and stream server-side wav files (File Source). Probably it is a good idea to add Recorder option to save files to server side in future, as well (important for android / mobile users).

7) old feature: bluetooth headset microphone support for android ticks the last bullet in mobile (as in mobile phone) comms.

https://sdrpp-brown.san.systems/

Overview of baseband compression: https://www.youtube.com/watch?v=dH-8xuz9nAA

DISCLAIMER

1) lossy baseband compression = controversial idea: your constructuve feedback is welcome. 

2) bugs expected as usual - PLEASE REPORT BUGS AND SUGGESTIONS.

3) releasing early without extensive field testing by myself - issues with current home antenna.

Possible bugs:

* some slowly accumulating timing issues with buffering can lead to eventual delays in TX. Start/stop RX to reset it. Under investigation.