PSR dataset improvement

[fmocking]

Hello, thank you for providing such a great dataset collection to the community. I was recently working on the PSR dataset and noticed some possible improvements can be made. Mainly, about maintainability and some more information.

1. It would be beneficial to keep the dataset up to date. For example at the time of the dataset publication, CASP 11 stage 2 was selected as a test set. I think this can be updated to a more recent version. This can require some versioning at the dataset level to make it consistent. It can be named according to the last full CASP name.
2. It is related to the last point, currently, it is challenging to extend it and keep it consistent. Maybe some guidelines can be helpful.
3. I couldn't find a way to tell if a sample is from stage 1 or stage 2. I'm not sure if I'm missing something but there is no information available for custom splits.

Again, thank you for sharing your great work.