docker: certificate generation + various improvments: - certificate is now auto-generated on first prosody launch is there is not already one - certificate generated on build is removed to avoid image-wide certificate - generated certificates are stored in sat_data - data image is now based on prosody which is itslef based on sat_pubsub - prosody configuration is moved to /etc/prosody/prosody_sat_cfg, and stored in sat_data - building order changed to adapt to new images hierarchy - libervia default configuration set to both without redirection (and with a security warning)

zone "<domain>" IN {
  type master;
  file "zone.<domain>";
};

zone "0.0.127.in-addr.arpa" {
  type master;
  file "revp.127.0.0";
};