Add bounding box support

[tymokvo]

Summary

• Add bounding_box module wrapping Bnd_Box and BRepBndLib
• Add tests
• Add bounding_box example

Description

I need to compute bounding boxes of OCC geometry for a project that uses opencascade. Thankfully, OCC has the BRepBndLib package that supports this already. This adds a wrapper for the BRepBndLib::Add method and the underlying Bnd_Box class on which it depends.

To support this and show how to use it, there are a few simple tests and an example that uses the viewer to show the bounded and bounding geometry.

One thing that I didn't understand, but that I assume is important to the underlying algorithms in OCC, is that the Bnd_Box has a small Gap value that is added to every dimension of the box. I decided to expose this as gap_vec to make it easier to work with in the rust side and tried to document it clearly.

[bschwind]

LGTM, thanks! I'd like to format the decimal literals in bounding_box.rs but I'll handle that.

[tymokvo]

Ah thanks! Sorry I missed those!

[bschwind]

No worries! I wish rustfmt had a stable option to format them so you don't even have to think about it. I think someone had proposed it but I don't know if it ever got implemented.