--  parameter 'broker_url' in plugin configuration now optional
    -   if value is not set, the current system ip and the default broker port (12900) will be assumed
    -   manually add  this parameter, if the sonos broker is not running on the same system

--  added optional parameter 'refresh' to plugin configuration (edit /usr/smarthome/etc/plugin.conf)
    -   this parameter specifies, how often the broker is requested for sonos status updates (default: 120s)
    -   Normally, all changes to the speakers will be triggered automatically to the plugin.
--  bug: if a sonos speaker was reported by the broker but was not declared in sonos.conf, an error occured