Reified Tags shouldn't be hard-instantiating Undefined Tag View

Summary: Specifically, when we reify a Tag from a Model, and then add a Default View for the Model, the Tag is now overriding it. That's wrong.

Not sure what the right answer here is. Maybe a new flag that says "This was originally a Tag", which tells the system to use the Undefined Tag View by default instead of the system default View? Then we could set that flag when we reify, and it is only relevant if there isn't a Default View set.