First pass at VALVE Validation

[beckyjackson]

This still gets a little hung up checking molecule, but it takes 45s to validate everything compared to the ~30 minutes that it was taking ROBOT.

The rules were copied from the original ROBOT validation rules. I had to add some imported terms to external to be able to reference them without VALVE complaining, and I added some of the external terms to core when they have MRO parents (so we don't have to have interdependent tables).

[beckyjackson]

TODO:

• add regex patterns for labels to datatype.tsv
• add checks for restriction levels
• check index table for distinct IDs
• replace current validate_template scripts with this