Handle view-fit case for distantly-placed model accompanied object that marks the coordinate origin

[xeolabs]

Some models that are placed far from the coordinate origin still have a simple bit of geometry that marks the location of the origin. This means that when we locate the camera so that all elements fit in side the view volume, we end up looking at empty space between the model and the origin.

Possibly fix with an option to exclude objects of certain types (or no type) from view-fit boundaries.

Or at least alert users in documentation, to ditch the origin marker object.