Users can change a Thing to a Model that they aren't allowed to Create

(Bug, Closed -> Fixed, Priority: Critical, Test Status: No automated tests yet , Reported By Bad Link: Thing 3y284oe not found, )
Security
Summary: Observed by Eric: Change Model isn't properly protecting the target Model.
Change Model should require two permissions -- you need to have Can Edit on the Thing, and Can Create on the new Model.