Use relative imports consistently

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Introduce a configuration error for better error messages

Not yet used.

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Break up overlong lines

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Finally move reporting to RunId and RunConfig

Reporting can be specific to an experiment, and thus, the run_id needs to know all the reporters.

Signed-off-by: Stefan Marr <git@stefan-marr.de>