Shadow Quality Manager

[Floris]

I created this widget because I love to play with shadows enabled.
But because shadows are costly for the cpu, I needed to play without them, not anymore!-

- auto adjusts shadow quality when average fps gets lower (or higher)
- maxQuality: 8192, minQuality: 2048
- can turn off shadows when quality gets below minQuality value. (default not enabled)
- default 8 fps difference is required before changing the quality