Improved Shadow Maps

[hadryansalles]

• [x] fix for switching between light types
• [ ] cascaded shadow maps?
  • [ ] for sun light
• [x] fix for spotlight behaving like point light
• [x] fix culling mode
• [x] some simple smoothing?
  • [x] hacked pcf
  • [ ] sub pixel jtitering when rendering shadow maps?
  • [ ] pcss?
• [ ] make spot light use single texture
• [ ] directional light shadows are looking weird
• [x] atmospheric model
  • [x] add sun light type
  • [ ] option for night sky? ...