use array refs instead of hash refs in Rules

[cooper]

Need to make a way to have multiple rules of the same type for a given element.

[cooper]

All the rules are implemented with the assumption that there will only be at most rule of a certain type for a given element. Therefore the entire element rule implementation needs to be rewritten.

[cooper]

Hmm, maybe instead of doing that, we should not merge the rule sets. Just enforce each of them separately. That would save a lot of time.