Document Gazebo Integration

[hamishwillee]

Currently we cover how to set up Gazebo/CSD in the Gazebo Quickstart

@lbegani questions for you ....

1. You recently updated Gazebo integration in Add custom parameters for Gazebo camera and provided test instructions:

   1) Start the simulator: make posix gazebo_typhoon_h480
   2) Open QGC 
   3) Select UDP Video Source in General Setting-> Video -> Video Source -> UDP Video Stream. Fill in UDP Port as 5600
   4) Compile the csd with gazebo and mavlink support
       `./autogen.sh && ./configure --enable-gazebo --enable-mavlink`
   5) Host the camera-def-gazebo.xml file in a http server (I have used apache)
          `sudo cp samples/camera-def-gazebo.xml /var/www/html/`
   6) Start the csd
       `./csd -g info -c samples/gazebo.conf`
   7. Select the "Cameras" dropdown in QGC
   8) Change the parameters in QGC and see the value set in the video frames (edited)
   

   • What documentation is required for this - I think just a new step in the gazebo setup stating where you go to find the parameters for the current camera right?

2. There is a new PR in Multi camera Support mavlink/qgroundcontrol#6186 - what impact would this have on Docs

3. At top of Gazebo Quickstart it says "Warning These instructions are in progress. At time of writing build without --enable-mavlink and connect on udp port 5600 (RTSP publishing not supported). To be reviewed 9 March 2018."

   • is that all still correct. If not, which parts have changed?

4. Your docs for Gazebo design are here. Is the design/structure useful? If so, can we get this doc updated to reflect how things are now?