WIP: split libraries from SFFs

Design is to support:

* SFFs
* fasta
* fasta and qual

Specific parameters such as barcode type will be sourced from db. Finalizing this will require touching a few other areas of the codebase and a db patch, which I'll get to as they become necessary.

~~**This is not tested, and not mergable yet**~~
We decided that we will only accept single fasta files if they come
from Sanger, so the name is fine. If you need more explanation, we could chat.