Only automatically center view when loading (not removing) geometry
Only automatically center view when loading (not removing) geometry

Previously the 3D view would be centred when you've got N geometries and
you *remove* N-1, which is just inconsistent and especially unhelpful
when scripting a user interface via the API.

JoshChristie/displaz,JoshChristie/displaz,JoshChristie/displaz,JoshChristie/displaz,JoshChristie/displaz