Adds the `ntuple_file` option to PyConf to configure the ntuple-writing
service.

- The "standard" preprocessor for `validateWithRef` (`ref_preprocessor`)
  removes everything before finalization.
- All tests should use `countErrorLines` with the "standard"
  `remove_known_warnings` preprocessor to check for errors and warnings
  in the entire stdout

Closes #5, #10, #13, #39, and #69.