Publish configuration and drone settings

[kbogert]

When interacting with the drone it is helpful to have configuration information, such as what euler_angle_max is set to and the ip address of the drone. At the moment, a lot of this has to be duplicated in other projects (see, for example, tum_ardrone) but it would be better if ardrone_autonomy would make the configuration info available over ROS, say using dynamic_reconfigure.