Three Stage shift

[Gfurst]

The idea is simple, have transition into three stages, or rather two separate night shifts, one for working night, and another sleeping time. That is to differentiate that time when its gotten dark but you're still active, from that time when you need to wind down and get sleepy. All considering that the red shift in color is supposed to wind down activity for sleep.

All it would be needed is a third set of settings (color temperature, brightness and time) for the sleepy nighttime, it could be optional in the configuration file only, in a way that for those who don't want to opt in, the application follows the schedule just the same as it already does.

[le-jun]

Duplicate of #552