AP_SteerController: move scaler onto integrator input

this should make integrator scale with speed

Pair-Programmed-With: Paul Riseborough <p_riseborough@live.com.au>
AP_Airspeed: reduce speed of autocal 

it was responding to noise too rapidly

Pair-Programmed-With: Paul Riseborough <p_riseborough@live.com.au>
Rover: changed default L1 period to 11