* Import attrs of profiles automatically with `defaultImport`.
* Refactor profiles to ensure all are functions returning a module.
* Add a suites.nix with collections of profiles.
* Add suites as `specialArgs` to modules.
* Add suite import to NixOS host.
Keep the README.md lean and use DOC.md for more detailed explanations. While
revising user documentation, a default `nixos` user profile was created, which
serves as a goood base example.