Implementation of a simple BoundingBox

[PyMarc2]

A BoundingBox is necessary to rapidly know the 3d extent of a structure, wheter it is a polygon, a solid or a scene.

The BoundingBox is analogous to the cuboid, it has x, y and z values.
It cannot interpret or nuance for any curve-like object, thus cannot be directly used to know if an object contains another.

The BoundingBox will be used for raytracing/intersections calculations and for the object-search algorithms

[JLBegin]

I approve the changes, but I would like an update on the bounding box property tests as discussed before merging.

[PyMarc2]

waiting for confirmation