Per request from Nathan, add an offset value to the job struct so we can construct a "global rank" that spans multiple jobs during dynamic launch operations. Store a new ORTE_DB_GLOBAL_RANK value for each process in the database, and ensure that we share our own value during connect_accept so both sides can see it.

This isn't being used yet - just enabling Nathan to do what he needs.

***** NOTE: any use of the OMPI_DB_GLOBAL_RANK database key must be protected by #ifdef OMPI_DB_GLOBAL_RANK as not all RTE's will define this key. *****