Add new informations about vo_short_names to pbsmon_json script

 - add information to json about short_names of vos, where resources of
   facilities exists

 NEED TO BE ADD AFTER MERGE:
 - need to add new required attribute (virt_vo_short_name) to service
   pbsmon_json
 - need to add info to changelog
Do we really want hash here? Wouldn't array be better?