Update to boxing algo for 'small' circles

If circles have radius 3 or less, we use a completely different
and much simpler boxing - simply the bounding box. At this size,
this box is more than adequate and _much_ faster than the standard
4-box attempt.
Changes to environment and engine code

Needed to accomodate the environment.switchView method for the
config to be able to switch to a new view. For this, it's much
more helpful if the environment keeps track of the engine and uses
that (along with its list of view definitions) to essentially
'reconstruct' itself when switchView is called.