[bennu-admin] Greatly improved System Info panel

  * Added Domain Browser functionality
  * System Info now shows more JVM information and allows Thread Dumps
[bennu-portal] Updated version of Pebble, solved issue with PortalResponseWrapper

  * response.getWriter() was being incorrectly called when nothing has been written
  * Performance tweak at MenuContainer: Match path, only then check access control
  * Also added a Portal Backend to handle Redirects