Allow fitting with perturbative charm (or any other basis)

Created by: scarlehoff

There were a few places where the flavours were fixed (which assumed charm was fitted), this basically propagates the information from the runcard, hoping that at the end it will be rotated to whatever is the correct thing wanted by the fktable.

Two things are missing here,

1. An actual basis (from a quick look, all basis in pdfbases.py are for fitted charm right?, so it needs to be added)
2. An actual check (at the moment I am acting as if the fktables would be just the same meaning that combination 1-2 for theory 53 is the same as for theory 65. Is that the case? (i.e., is any reshuffling of the PDF output needed from one theory to the other?)

In any case, these were the basic points I mentioned in #1002 (closed) blocking the perturbative charm fit from the n3fit side.