Sky lighting (interface)/0.99.5a

Sky is a retractable set of functions from Render's light panel.

Uniform lighting
Enables a distinctive sky menu, with:
 * intensity scale from  to
 * sky light color box

Atmospheric scattering
Enables a distinctive sky menu, with:
 * a Rayleigh
 * density scale from  to
 * color box
 * a Mie
 * phase setting from  to
 * density scale from  to
 * color box
 * an Ozone
 * density scale from  to
 * color box

Image based lighting
Enables a distinctive sky menu, with:
 * intensity scale from  to
 * image rotation scale from  to
 * the ability to choose which HDR image to use as scene lighting