Add gazebo-bluerov2 in ardupilot

[patrickelectric]

It appears that libArduPilotPlugin.so and libArduCopterPlugin.so do ardupilot-gazebo bridge,
the first one is a new concept done by @khancyr, the second is an old plugin that apparently will not interact with underwater vehicles.

[khancyr]

The ArduPilotPlugin is the generic version and is better. I hadn't time to finish publishing all my works on gazebo plugin. Here is the lastest usable version : https://github.com/khancyr/ardupilot_gazebo (and the simplier way to install it ! )

[patrickelectric]

Thank you for reply @khancyr !
Yes, it's already running here with worlds/iris_arducopter_demo2.world, congratulations with the great work !
I'll start to study it and integrate with my BlueRov model.