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.
magic numbers!