AP_InertialSensor: fixed example build
AP_NavEKF: Default parameter adjustments

Bring Plane glitch protection thresholds into alignment with copter and
rover
Slight increase in accelerometer bias process noise to prevent bias
estimate divergence into limits (Rover and Plane only as Copter does not
seem respond as well to this change)
effective increase in threshold on divergence test to allow increased
margin for bad GPS velocities
AP_NavEKF: Add protection for accel bias estimation errors

Don't do bias estimation if tilted by more than 60 degrees to prevent scale
factor errors affecting result unnecessarily.
Prevent Kalman gain from having the wrong sign due to numerical errors
associated with small process noise values.
Allow smaller Z accel bias process noise values to be set
Plane: prevent a bad glide slope when first entering auto

we need to ensure that prev_WP_loc is not used as it could be
completely different from current_loc. As a precuation, this also sets
up next_WP_loc so that when the set_next_WP() is first called that
prev_WP_loc is set to current_loc