Added new callback class that enables routing both the locally recorded
and playout audio data to external module.
A factory method that creates an AudioDeviceModule instance that also
registers the AudioTransportCapture with the device is also added.
BUG=webrtc:7337
R=solenberg@webrtc.org
Review-Url: https://codereview.webrtc.org/2753453002 .
Cr-Commit-Position: refs/heads/master@{#17570}
