Implemented the scaffolding for basic Foldable support.
Folding is now zone-aware, at its most basic level. It know understands that higher leaf nodes correspond to a large sequence of the wrapped data instances.
Fixed the folding to right-fold properly, as opposed to implicitly foldl-ing.
Folding is in! Border control seems to properly work, though I wouldn't be surprised if there are bugs.

foldr should automatically decompose the entire tree into regions and then decompose the regions into lists of elements for proper folding.

Eventually the regionlist functionality will be exposed to the user, since it has some powerful miscellaneous applications. That's why it's been reified into its own function.