Clean up all the (.*)evolve(.*)(fit)? codes

Created by: Zaharid

We have a bunch of these and I have completely lost track of what each one does. I do know we have had many bugs associated to them. As far as I can tell the only one that is documented in the new docs is

https://docs.nnpdf.science/search.html?q=evolven3fit&check_keywords=yes&area=default#

The other ones being

https://github.com/NNPDF/nnpdf/tree/master/nnpdfcpp/src/revolve/src https://github.com/NNPDF/nnpdf/tree/master/nnpdfcpp/src/evolvefit/src and to some extend https://github.com/NNPDF/nnpdf/tree/master/nnpdfcpp/src/fiatlux/src

Questions:

 - Can we use that script to get rid and get rid of all the other ones while still being able to do take this PDF and this theory and evolve up.   * If not what is needed to extend them?   - Relatedly, what is the plan for producing stuff like the nf variations (incidentally I don't recall a single occasion when those didn't have bugs)?   - If we do need the old stuff, can we document why?