With Wayland KWin needs to provide certain services, which were provided
before that by the Xserver. One of these is gamma correction, which includes
the - by many people beloved - functionality to reduce the blue light at
nighttime. This patch provides the KWin part of that. It is self contained,
but in the end will work in tandem with a lib in Plasma Workspace and a KCM
in Plasma Desktop, which can be used to configure Night Color.

* Three modi:
** Automatic: The location and sun timings are determined automatically
   (location data updates will be provided by the workspace)
** Location: The sun timings are determined by fixed location data
** Timings: The sun timings are set manually by the user
* Color temperature value changes are smoothly applied:
** Configuration changes, which lead to other current values are changed
   in a quick way over a few seconds
** Changes on sunrise and sunset are applied slowly over the course of few
   min...