Add shutdown port, so can receive a shutdown request via HTTP GET

[apatrida]

Added this, with default configuration:

  # Shutdown options
  shutdown: {
     httpPort: 9983
     httpHost: "0.0.0.0"
     # if password is not set, shutdown is not enabled.  Make this a secure password!
     password: ""
     gracefulDelay: "30s"
  }

If password is not configured, shutdown port will reject the request.

from the updated README:

Restart / Shutdown

Solr-Undertow listens on the configured shutdown HTTP port (defaults to 9983) for a GET request, single parameter of password which must be set to a value matching the configured password.

If the a shutdown password is not configured then a 403 forbidden error will be returned. If the password does not match, a 401 unauthorized error will be return. Otherwise on success a 200 HTTP response, and on timeout or other error a 500 HTTP response (although the VM will still exit). See the configuration defaults file for the shutdown section.

[apatrida]

Added in 1.4.0-RC1 release

[magicdude4eva]

Awesome - thank you. Find my startup/shutdown scripts and JVM tuning options in this GIST for possible inclusion - https://gist.github.com/magicdude4eva/3b5fec150fbcaafdc34c

[apatrida]

Tracking your examples scripts as #25