* Added a pure virtual render() function to FGATController that can be used to implem...

* Added a pure virtual render() function to FGATController that can be used to implement traffic visualization
* Allow position and intentions to be monitored and updated by the Startup controller
* Added a "parent" pointer to the startup controller to allow communication with the groundnetwork.
* Implemented a render() function for the Startup controller
* Renamed "FGGroundNetwork::getRenderNode() to FGGroundnetwork::render()