Inner cone visualization for spotlight was added, as well as drag
handles to adjust inner and outer cone angles and fade.
Fade handle adjusts fades in order: quadratic, linear, constant.
If a specific fade value is zero, the next one in list is chosen
for adjustment.
Change-Id: I921936d9782de511558bc6c24cfa0953cce494f0
Fixes: QDS-2038
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>
