• if 'MDBaseServer' in enabled and there is no specific VirtualHost for a domain, the
  base server config is considered the relevant one for deciding ACME support. This
  is most relevant for the 'tls-alpn-01' challenge, see issue #150).
• MDMessageCmd is now invoked with 'installed' when the certificate is actually becoming
  active at server startup/reload. Different to all other messages, this one is invoked
  while the server is still root and has according privileges. (Hint: you may use this
  to copy a certificate+key to another application's preferred location/format.)