Make Skybox work with TUFX

[Lisias]

As suggested by Fellow Kerboaut rheaunderstars on Forum:

the dynamic skybox dimming feature has a setting for maximum sky brightness. But I'm using TUFX to control my camera's exposure. I do want the dimming, but I don't want it to be dynamic. Currently there isn't an option for this in DOE. So I was thinking it would be nice to have the max brightness setting be separate from dynamic dimming, so that you can adjust the brightness without needing it to be dynamic. Alternatively, you could add a minimum brightness setting, which could be used to basically do the same thing.

My first take:

• Add a slider on the Settings for the minimum dimming (and code for it)
• Add a small checkbox on the Settings to lock both dim sliders, making them be equal to each other.
  • prioritize max bright (ie, when activating the checkbox, copy max into min)
  • When deactivating the checkbox, set minimum to zero automatically