I want to have _some_ settings set outside my NixOS configuration, so keep the config-file writable.
See previous commit for the defaults.
Attribute sets compose better than lists, it was a mistake to use a list in the first place...
Let's consolidate all modules under one path, so that NixOS, home-manager, and nix-darwin (if I ever end up using it down the line) would go under the same folder.
