Add support for name grouping import/export
* src/GrampsDb/_GrampsDbWriteXML.py: write group table out
* src/GrampsDb/_GrampsBSDDB.py: group table is no sec table, init it
together with primary tables!
* src/gen/db/base.py: obtain grouping keys
* src/gen/db/dbdir.py: group table is no sec table, init it
together with primary tables!
* src/gen/utils/dbutils.py: grdb -> grdb copy of grouping table,
copy mediapath.
* src/gen/proxy/proxybase.py: obtain grouping keys, add missing
bookmark methods
* src/gen/proxy/dbbase.py: add obtain grouping keys method
* src/GrampsDbUtils/_ReadXML.py: read in group table
* src/plugins/ReadGrdb.py: read in group table
svn: r9464
