This was, uh, half-implemented in csv.py's collect_csv, but completely
ignored in read_csv/write_csv. Adding support to read_csv/write_csv
wasn't too hard, so maybe we should keep this?
There's an argument notes should not be included in csv output, as the
nested commas (for multiple results) can make a mess of csv's simplicty.
(There's a different argument that csv is a terrible format, but I'm not
sure I agree.)
But for now, including notes doesn't seem to harm anything.
---
Note this also includes a fix for filtering empty notes in csv.py's
collect_csv.
Christopher Haster
ecc72e3dba