Add Visual Motion Detection

The camera now creats a motion detection thread.  This thread attaches
to a camera preview surface onPreviewFrame.  I had to attach to
onPreviewFrame for two reasons.  First,
if you use onTakePicture there is a shutter sound and we want to be
silent, there is no way to turn this off for privacy reasons.  Second,
the time it takes to process
the onTakePicture even is too long, the previewFrame is almost instant
so we don't have to wait for a long period of time between frames to
check for motion.

We can latter add a callback to the MotionDetection Class that will be
called to do certian things once motion is detected on the camera, ie.
take a photo, start recording video

The RgbMotionDetection Class simply creates bitmap of the image from the
onPreviewFrame callback and compares it to the bytes of the previos
frame.  If the threshold is
large enough then it decides there was a change in the image.  Note:
Latter we could even add functionality to paint these bits in red to
outline the movement, just
a quick though of a possibility.

etc...

References:
* http://developer.android.com/guide/topics/media/camera.html
* http://developer.android.com/reference/java/util/TimerTask.html