Update EKF estimator to most recent version from Paul Riseborough

@sjwilks This is the last bit in the puzzle to get Lidar / flow urban localization going. You will need to implement the equivalent of this block for the flow sensor:
https://github.com/priseborough/InertialNav/blob/optflow_merge/code/main_closed_loop_float.cpp#L379-L458

I did intentionally hold off on that one. I have no bandwidth to debug this and it doesn't need estimation knowledge - its pure library integration and sign checking.