Request echo cancellation from PulseAudio on mic and speaker streams
WIP because:
- needs !25 (merged)
- needs device-specific parameters for optimal filtering; like in sebastian.krzyszkowiak/wys@0d8bbfd0, but I don't think Wys is the correct place for it; PulseAudio should pick it up with environment variables which seems like a reasonable solution, but I have yet to try that
Closes: calls#62 (closed)
Edited by Sebastian Krzyszkowiak