to using new birth/death reference approach.
* src/GrampsDb/_GrampsDbBase.py (commit_person): Simplify updating
of the custom event roles.
* src/GrampsDb/_WriteXML.py (write_person): Use methods to get
birth/death ref, not raw attributes.
* src/RelLib/_Person.py: Convert to using birth and death ref
indices.
birth/deat reference; use methods to get birth/death ref, not raw
attributes.
svn: r6762