Move standard fields for the 4 file types into a yml file from the check_fields.py code

[jdpye]

The 4 archive types and their required fields are inline in the code right now, and it could be cleaner to separate them into definitional YML and then reimport them in the check functions.

yaml.load() will bring in a dictionary and can be crafted to produce the same structures as are expected by the function presently.