- list_vms in Clouds now returns ServiceNodes
 - added tests for controller
 - added multiple clouds to controller constructor
 - from now on we must use '__' at the beggining of internal configurations
 - default cloud is set by either first one or by starting with 'default_'
 - realised that there was already a proposed solution using a 'CLOUDS'
   option in 'iaas' section
 - controller supports multiple clouds