Implement CAMERA_MSG_PREVIEW_FRAME callback
Also does better work detecting pixel format for video frames, depending on the
mode that camera is intended to be operated with.
Change-Id: Idb2dfc7c0a79e81eff58f83a14af769afc713096
These two tasks (starting the camera device, and starting working thread that pulls frames
from the started camera device) should be clearly separated, and should not be combined in
one method (as it was with the 'startCapturing' method).
Change-Id: I779bee924d99d9a87257c6b76791545b76795e72
