Add FeatureExtractor interface for processing channels and extracing features. Add an AubioFeatureExtractor for processing audio streams with Aubio.
Create an AubioFeatureExtractor for every deck.
Create ClockControl in EngineBuffer instead of BaseTrackPlayer.
Add beat_active_this_frame control.
Change Aubio buffer/hop size.
Add EngineBufferFeatureExtractor.
Use AubioFeatureExtractor for passthrough processing, EngineBufferFeatureExtractor for internal audio.
Use COT member instead of COT*.
Add AubioFeatureExtractor to passthrough inputs.
Print Aubio beats.