Adding initial README. I need to push this first before I can edit it online.

src/VideoStreaming/README.md

+# QGroundControl
+
+## Video Streaming
+
+For supported platforms, QGroundControl implements an UDP RTP video streaming receiver in its Main Flight Display. It used gstreamer and a stripped down version of QtGstreamer.
+To build video streaming support, you will need to install the GStreamer development packages.
+
+TODO: Complete this once the PR is through.