Changes add alpha skybox with lighting.

Skyboxes now work with scatter skies and time of day, and have a color and exposure control.  Cloud layers can be set to be in front of or behind the skybox.  Normal skyboxes will not display properly unless the material property is set to emissive.

Blog post with example screenshots and a skybox found here:
http://www.garagegames.com/community/blogs/view/22265