We have properties that have been renamed—some even twice—leaving a mess of legacy names that are still supported, but create confusion for users.

Note: It seemed as though these names may already have been removed from the docs. In that case, there is no problem, and we can deprecate with impunity.

Definition of done: There is one and only one name per regionprop. If names are already undocumented, go ahead and remove them completely. If they're still mentioned in the docs, deprecate them, and remove any mention of them from the docs.