AirSim ROS with AngleRateThrottleControl Interface and packed UE4 project

AirSim ROS with AngleRateThrottleControl Interface and packed UE4 project

1. add packed UE4 project for linux
2. add airsim_ros_pkgs to workspace
3. add angle rate throttle control interface into airsim_ros_pkgs using AirSim C++ API

City Park UE4 project with AirSim plugin

1. Created a UE4 project and added the AirSim plugin.
2. Added the official Python examples.