Incorporating add_carbon to snakemake

[anushka255]

• Add carbon at this stage is optional and set to false. In order to generate the carbon files and incorporate those in structural_prior, run the snakemake workflow with flags --config add_carbon=true

[vineetbansal]

I'd blanked out on simply using enumerate along with if i>0 to go past the first item in a generator easily. With this we don't need fancy awk stuff (which would again have been locale specific anyway).

The only difference in the data files is the addition of new rows for the addcarbon model towards the bottom in addition to the existing ones. Tests pass fine - the one without add_carbon is now removed, and renamed as the original one for structural_prior_CV