Can we efficiently represent a Taxonomy as a PublishableEntity with Dependencies?

[ormsbee]

I've said in the past that the way we model versions for things like containers would be inefficient for very large things like Taxonomies, because it would require rewriting all the parent/child relations on every version. But I belatedly realized that we could model Taxonomies reasonably efficiently if there are many levels of hierarchy and only a few of them are changing at a time. We'd use the same tricks for when we have unpinned parent/child dependencies.