createView threw on style 'snow', so an embed host or a
show_in_gods_eye_view call holding a view from before Snow was retired
was refused outright, camera and layers included. viewFromParams read
style=snow as the recipient's own style, while the app opened the same
link on Normal.
Both now read a retired style as Normal; truly unknown names still
throw. The retired list moves to a browser-free module shared by the
view API, the share codec and visual settings.
