• New directive MDMatchNames all|servernames to allow more control over how
  MDomains are matched to VirtualHosts.
• New directive MDChallengeDns01Version. Setting this to 2 will provide
  the command also with the challenge value on teardown invocation. In version
  1, the default, only the setup invocation gets this parameter.
  Refs #312. Thanks to @domrim for the idea.