The variable was necessary when multiple playbooks could have
potentially tried to manage a shared `devture-traefik.serivce` systemd service
and shared `/devture-traefik` directory.
Since adcc6d9723, we use our own `/matrix/traefik`
(`matrix-traefik.service`) installation and no conflicts can arise.
It's safe to always enable the role, just like we do with all the other roles.
We had something like that on the Server Delegation how-to page,
but it's better if we have it on the SSL certificates page.
Relocated there and improved linking.
Fixes#94 (Github Issue)
Adds support for managing certificates manually and for
having the playbook generate self-signed certificates for you.
With this, Let's Encrypt usage is no longer required.
Fixes Github issue #50.