Rename state on address to principal_subdivision

[AlistairNorman]

Desired Behavior

The term state is not right for most countries. In addition to that the way we're fetching data from Carmen might not match the correct subdivision level. In order to resolve this, we can rename the column while providing a deprecated alias to preserve current behaviour which can then be removed in a future major release.

[AlistairNorman]

I realized there are a couple more questions than we had originally talked about here. I was just thinking about methods on the address but there's the model and API requests/responses to deal with. Do we want to rename everything? For the API I imagine we would emit and accept both for now. Do we want to alias the whole Spree::State class? cc @adammathys @jarednorman