Feature: Boolean Operations for `BOX_2D`

While proper boolean ops between the different more advanced geometry types definitely would require a `GEOS` module, I'm confident that implementing them for planar 2-dimensional bounding boxes, like the `BOX_2D` native type would be both useful and comparatively easy.

1. We should make sure to follow the [DE-9IM](https://en.wikipedia.org/wiki/DE-9IM) semantics.
2. We should be careful of floating point comparison and precision issues.
3. We might also add a basic point-containement function operating on the `POINT_2D` type.