Add Brick shape for ContactGeometry

This is a first installment in proper geometry handling for convex meshes that can be used with either compliant or rigid contact. 

- Added convex mesh features to Geo::Box.
- Added penalty force generator for Brick-HalfSpace Contact.
- Added adhoc test ContactBrickTest showing mesh topology and displaying generated forces & force details.
- Misc. contact cleanup.
> really minor, an empty separator line between the functions may make the declarations easier to read?

Done. Thanks, Kevin. There are lots of other places when I should do this too. I'll fix as I run into them. Regards, Sherm