Implement contains for BoundingBox

[MicahGale]

Description

Implement __contains__ for BoundingBox containing either a point, or another BoundingBox. This means that users could then write:

if point in box: or if little_box in big_box.

Alternatives

It is possible for users to accomplish this currently but requires some clever coding to avoid becoming difficult to read:

def in_box(point, box):
   for min_p, p, max_p in zip(box.lower_left, point, box.upper_right):
     if p < min_p or > max_p:
        return False 
   return True

Compatibility

This would be an enhancement, and would not alter the behavior of the existing API.

There is a risk though that users will misinterpret the results. A point in the bounding box of a volume may be in the volume, but not necessarily. A user could misuse this information and create problems for themselves. Also a small volume's bounding box can be completely contained in another volume's bounding box, and be completely outside that other volume.

[MicahGale]

Turns out this was added for points in #2759 e0d0381, or 0.14.1dev. I will still implement this for nested bounding boxes.