[New commondata format] FTDY

Created by: scarlehoff

I'm reopening #1610 here @tgiani This is just a rebase of your commits there.

These metadata.yaml files however contains some errors (and some things that we might want to change?)

1. The npoints field in hepdata. Do we need this field @enocera ? (if so I'll add it to the reader)
2. The theory field must always come with an operation even if it is NULL
3. The FK_tables are actually a list of list.

So, the theory right now is:

theory:
   FK_tables:
     - DYE605

but it should be

theory:
   FK_tables:
     - - DYE605
   operation: "NULL"

(this is due to some FKTables being a concatenation of grids now)

Point 2 is a bit silly in hindsight but for now it is like that...