Brightness can be controlled by dragging on the brightness indicator
arrow of the light gizmo in 3D edit view.
Change-Id: I317f5ee08b59bcc0bebf3fdf59861df15ef13c84
Fixes: QDS-2039
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>
Directional light model was made constant size, as it doesn't have
actual physical presence.
Spot light cone now shows the cone angle correctly and the length of
the cone is calculated so that 5% of the brightness reaches the
center of the cone bottom.
Area light rectangle matches the area of the light.
Point light mesh changed to three perpendicular circles.
Same formula for size of the circles used as for spotlight length.
All light types share a common brightness indicator arrow.
Task-number: QDS-2037
Change-Id: I534dbcda9cfa2a7768c2537868ba83818979b250
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>
