Applications for the AR.Drone

Currently, there are three applications:
 - Keyboard teleop
 - PS3 teleop
 - Navigation. Converts the Navdata2 message into /imu_data and /vo (For use with robot_pose_ekf).

Notes:
This depends on the ardrone_autonomy package.
You can find it at https://github.com/AutonomyLab/ardrone_autonomy

TODO:
 - Teleop:
   - Less annoying keyboard control.
 - Come up with other apps