Improve rendering

[JunePrimavera]

Our rendering code is very limited right now.

• Supports inverted-cube atmospheres
• Supports rendering Gas Giant's rings
• Supports large planets that may extend out of render distance
• Some kind of LOD for distant planets to appear on the skybox
• Easier to use than our current setup (Especially when it comes to textures)

[Haskellered]

Basic ray-casting could be a solution to this.