Include replication Bayes Factor as outcome

Separating this from the unwieldy #4 which we can hopefully close soon.

Replication Bayes Factors would be a helpful alternative success criterion - introduced [here](https://link.springer.com/article/10.3758/s13428-015-0593-0#Sec6) with code available [here](https://osf.io/cwqn7/?view_only=) - but the code is not entirely clear, or neatly packaged, and the copyright is unclear - so this is about more than copy-pasting.