Implement visualization output

[Sebdar]

The visualization node (monitor) requires a video stream to work. In the current deepstream (jetson) implementation, the camera feed is directly fetched from the camera, with no means to publish it to a ROS topic.

The feature can be implemented one of two ways :

• Add a GStreamer pad to publish images to ROS
• Replace the input pad by a ROS listener, and revert back to the jetson_camera node for the image publisher