Not every option is exposed by redshift/gammastep parameters, for
example gamma options are only exposed in configuration file. So this
PR refactors this module to generate a configuration file and pass it
to the redshift/gammastep using -c parameter.
This is a breaking change since there is no support for some of the
older options like `extraOptions`, but unless you use `extraOptions`
it should work without changes.
Nowadays services.{redshift,gammastep} modules are really similar. They
should, since Gammastep is a fork of Redshift with the main objective is
to support Wayland.
So instead of trying to maintain two separate modules, this commit unify
the options in lib/options.nix file, making the implementation of the
module itself ends up being really simple (just calling the common
options with the necessary parameters to differentiate between them).
