viewer.zoomTo creates strange camera conditions

@bagnell can you look at this for 1.11?

For example, run http://localhost:8080/Apps/Sandcastle/index.html?src=Spheres%20and%20Ellipsoids.html&label=All
- ~~Zooming out over rotates.~~ Fixed in #2863
- Middle mouse drag seems to be locked around the center (same in 1.10, but are we sure we want this?)

Reproduce the remaining middle-mouse behavior using the Sandcastle Spheres and Ellipsoids URL, starting from viewer.zoomTo and the camera interaction path. Compare the behavior with 1.10 and determine whether locking the drag around the center is intended; the work is done when that behavior is resolved or its intended status is explicitly established.

Written by the indexing model from the issue text.