Bounding Box Trees

[julialongtin]

Instead of having one bounding box, establish a tree of bounding boxes to more closely fit the object. get the renderer to consume this tree, rather than a simple box.

next: make the intermediate form generation system mark "boring regions" that are contained inside of primitives, and can be skipped.

next: make the intermediate form generation system have more optimized forms of the big function that applies within different bounding boxes.