Do not hard code all values, instead configure them within home.nix.
This is more for learning purposes.
But port and allow might also be changed more frequently in general.
home-manager doesn't provide a systemd service itself.
That's why we build one ourself.
That also revealed a change in our directory structure.
The structure is now documented within readme.
Move all packages to home.nix and remove `my-packages` derivate.
Also define dunst service and remove readme entry related to
configuration and services. Those are now maintained via home-manager.
The "update" section in readme got updated to reflect new home-manager.
Daniel Siepmann