Changed auto scaler math to use more double precision math to improve
scaling accuracy when camera is zoomed far or gizmo is far from origin.
Change-Id: Ic3020bbf159c0d5d090af9c9b8e8a4aa372d2406
Fixes: QDS-1528
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>