AP_AHRS : Tidy up logic used to enable synthetic sideslip fusion
DataFlash : Change to more descriptive EKF logging names
AP_NavEKF : Remove ineffective numerical divergence checks
AP_NavEKF: clean up unused variable lastDivergeTime_ms
Replay : Remove unused numerical divergence metric
Replay: clean up unused variables deltaGyroBias and divergeRate
DataFlash : Remove unused numerical divergence metric
AP_NavEKF: Set prevDelAng after using it
DataFlash: fix bug in ekf gyro bias logging
AP_NavEKF: Split getAccelBias into getAccelZBias and getIMU1Weighting
DataFlash: use new interface functions for EKF IMU weighting and accel biases
Plane: removed unused function