OP-1506 Wrong_display_alt_speed : Fix wrong scale display for speed and altitude. Hide scales (because do nothing) if no units defined in options km/h, m/s, knots, miles/h (speed) or meter / ft (altitude)
OP-1506 Auto-select Vsi unit and scale from altitude unit : m/s or ft/s
OP-1506 Speed, altitude and vertical speed units in cyan
OP-1506 Remove Svg gradient, now draw in qml (linear from middle). Remove Vsi scale background.