Philippe Gorley authored Jan 18, 2019 and Philippe Gorley committed Feb 01, 2019

Adds a signal that sends the linear RMS level for a given ring buffer.
The signal must be turned on via the API and can be turned off when
needed.

Adds an audio preview so the mic can be read. Call startAudioDevice and
stopAudioDevice to initialize and stop the audio layer.

Change-Id: I6a71ef87ee805a6d4bfa824fa901dd638e8cbd65