AP_NavEKF: updated tuning parameters
AP_NavEKF: added logging for EKF1,2,3,4 data flash messages
AP_NavEKF: fixed merge error
AP_NavEKF: bug fixes and robustness enhancements
AP_TECS : modifed to use inertial nav height and vertical velocity if available
AP_NavEKF: Added parameters to tuning list, improved zeroing of variables
AP_NavEKF: Improved health outputs
DataFlash: fixed build
Copter: fixed non-EKF copter build
DataFlash: fixed merge error
AP_NavEKF: fixed merge error that inverted static mode
Dataflash: fixed merge errors on gyro bias  & EKF4 logging
AP_NavEKF: changed sqrt to sqrtf