Inertial Navigation for PX4 and Pixhawk

This is an implementation and further development of the Extended Kalman Filter  algorithm presented in  https://github.com/priseborough/InertialNav.

It has had some flight testing on PX4 installed in a Skywalker X-8 and a Pixhawk installed in a X-5 airframe with good results. Link to data from most recent Pixhawk test in an X-5 airframe below:

https://drive.google.com/file/d/0B6YbG6fDf0m4X01Vd0RrWEpBM00/edit?usp=sharing

It has also had very limited flight testing on an Iris quadcopter running a Pixhawk.

Development has started to add optical flow measurements to the filter for future enhancements.