redundant, call in onPause
* Move receiver to DecodeThread
* Let CameraManager handle Camera.previewCallback to simplify message sending between handlers
* Remove unused millisecond timeout in qrlib Receiver
Give progress update messages an id
layout weight not necessary for surfaceview
Make displayUpdate handler static to remove the potential leak found by lint
Remove hasSurface flag and manage camera open/close from surface callbacks.
Note we have to force surface to get destroyed onPause otherwise application won't destroy surface whenever it exits from the power button
Open camera on new thread so PreviewCallbacks are handled off the main UI thread