duplicate_foreach with event_handler

Hi,

I need the ability to use the "duplicate_foreach" property with the item event_handler.

see below for an example:

define service{
   service_description  PRC_$KEY$
   use                  linux-nrpe-service
   register             0   
   host_name            linux-nrpe
   check_command        check_nrpe_args!check_procs!$_HOSTPROC_WARN$!$_HOSTPROC_CRIT$!$KEY$
   event_handler       launch_nrpe_args!launch_procs!$KEY$!restart!
   duplicate_foreach    _prc
}

By default the $KEY$ for event_handler is not instanciated.

If we look further in the shinken code, there's a place where this can be done easily (objects/services.py).

# Here is a list of property where we will expand the $KEY$ by the value
_the_expandables = ['check_command', 'aggregation', 'service_dependencies']

just add 'event_handler' to the list to do the job.