Atmosphere shaders

This is my shader work for atmosphere shading : 

![Alt Text](https://dl.dropbox.com/u/11319604/screenshot-20121229-211928.png)

###### Features:
Atmosphere scatter
Colorful sunset
Thinner fogging wich gives you a great view 
Increase light abit beyond the the dot product so ground doesn't get dark until sun is set (also for non atmosphere planets)

Some progress and shots from :  http://spacesimcentral.com/forum/topic/3175-extending-atmosphere/

At your mercy for review.