move down jobid,vpid from ORTE to OPAL layer

opal_process_name_t is now an union of :
 * opal_identifier_t (id)
 * opal_proc_name_t (name)
and orte_process_name_t is typedef'ed to opal_proc_name_t

the OPAL_NAME DSS type was introduced in order to correctly pack/unpack
an opal_process_name_t on an heterogeneous cluster

@rhc54 @bosilca this is working proof of concept to move jobid/vpid from the ORTE into the OPAL layer