This change introduces a new component - ColorManager that is
responsible for color management stuff.
At the moment, it's very naive. It is useful only for updating gamma
ramps. But in the future, it will be extended with more CMS-related
features.
The ColorManager depends on lcms2 library. This is an optional
dependency. If lcms2 is not installed, the color manager won't be built.
This also fixes the issue where colord and nightcolor overwrite each
other's gamma ramps. With this change, the ColorManager will resolve the
conflict between two.
Currently in order to load an Xcursor theme, kwin uses libwayland api,
which looks really awkward because of the way how the compositor talks
to itself via the internal connection.
The main motivation behind this change is to limit the usage of kwayland
client api in kwin.
