The long-deprecated (since Ansible 2.4) use of include is
no more.

We always skip at least one of these tasks, depending on which
SSL retrieval method is enabled, so it could have been confusing why.

Fix for d28bdb3258.

We were only supposed to install openssl when the self-signed
SSL certificate retrieval method is used, not always.

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.