bugfix: inputs/*/Source/data.csv for new-style datasources: need to include a blank row (plus a blank header) so that the metadata values are imported at least once instead of zero times, now that there is an installed staging table that will be iterated over. the blank row did not used to be necessary, because db_xml.put_table() has a special case for metadata-only tables with no installed table, which avoids iterating over the table's rows.