* src/GrampsDb/_WriteXML.py (dump_child_ref, dump_person_ref): Add
methods.
* src/RelLib/_ChildRef.py (ChildRef.set_mother_relation): Adapt to
new types;
(ChildRef.set_father_relation): Adapt to new types.
* src/RelLib/_GrampsType.py (GrampsType.get_custom): Add method.
(GrampsType.set): Allow setting from the same class instance.
(GrampsType.is_default): Add method.
svn: r6358
