Add a convenience video source for live sensor streams
Add a convenience video source for live sensor streams

The live stream source simply makes sure to instantiate a Grabber
source with an OpenNI grabber, configured to capture the default
sensor's stream.

This is a convenience class, when it is important to get a "live"
sensor information source.

mlalic/lepp2,sahandy/lepp2,mlalic/lepp2,sahandy/lepp2