Dynamic Illumination

Adds two new lighting buttons for Dusk and Dawn, and provides config settings to change the light color for Day/Dusk/Dawn/Night.

Also adds a darkness threshold to enable/disable global illumination (ie: during "Night" global illumination is turned off, at other times it is on)

Color and Darkness level can be tweaked for each time.

This is only tested with DND5e, but only interacts with the Scene Darkness and Global Illumination setting (and the core scene color flag), so it should work with any system.