toggleDataView tweak
CLDRegister3D, a define and sufficient features to do

The audience camera 3D registration is far from perfect, but it’s now
good enough. At least. Grr.
Rotation state per subject

…is what’s needed, but it’s a load more code than the method static var
‘Add viewpoint’ fixes

since new view menu items - index set from title, not hardcoded
scale restored - pov.camera.orthographicScale needed storing in
addition to pov.transform
for restored documents - readFromURL restores mutability of
freeSceneViewPovs