bugfix: inputs/*/Source/: use installed staging table (with blank-line data.csv) in order to also work with new-style import. this also fixes a benign diff between the by-row and by-col test outputs, where row-based import would not import the Source/ entries because there was not at least one row in the input. note that in order to ensure that all datasources are properly run, you need to check `svn st|sort` against the datasource schema names to see if any are missing.