Fix fine classes in trec dataset
_The documentation is not available anymore as the PR was closed or merged._
This PR:
- replaces the fine labels, so that there are 50 instead of 47
- once more labels are added, all they (fine and coarse) have been re-ordered, so that they align with the order in: https://cogcomp.seas.upenn.edu/Data/QA/QC/definition.html
- the feature names have been fixed: `fine_label` instead of `label-fine`
  - to sneak-case (underscores instead of hyphens)
  - words have been reordered

Fix #4790.