Add an executable and config to quickly dump GN2v01 scores

I've renamed the previous config we used to test the hashing EMPFlow_kfold.json to EMPFlow_hash.json.

Then I added a new executable and config *_kfold, which dumps GN2v01 scores. The config in particular (configs/EMPFlow_kfold.json) is designed to be very lightweight, it doesn't save any track or SV info, so it runs pretty fast and it fast downstream when making plots etc (see #123).

cc @nekumari, this should be good for you to study NNJVT