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.
Night Color adjusts the color temperature based on the current time in
your location. It's not a generic color correction module per se.
We need a central component that can be used by both night color and
colord integration to tweak gamma ramps and which will be able to
resolve conflicts between the two. The Night Color manager cannot be
such a thing because of its very specific usecase.
This change converts Night Color into a plugin to prepare some space for
such a component.
The tricky part is that the dbus api of Night Color has "ColorCorrect"
in its name. I'm afraid we cannot do that much about it without breaking
API compatibility.
