epoch.

Avoids memory overhead by only combining up to 100 steps into one epoch,
and not changing anything when using only 1 replica (i.e. on CPU).

Polarised Jet commondata implementation

Adds integrability datasets for DV and DV3

Allow for F1 FKtables in G1F1 ratio

Polarised scale variation theories

Merge branch 'polarised-scale-variation' of https://github.com/NNPDF/nnpdf into polarised-scale-variation