dataloadtool_export(): Add password-setting callback support.
(add comment)
(factor out duplication)
members_to_cidb_dataloadtool: Expose password callback option.
Strip the `pytype` namespace declarations, too.
Test without member.raw_password set, and improve handling.
Merge pull request #8 from pjdelport/feature/cidb-export-password-callback

Add a `--password-callback` option to the CIDB export command