Can't set the Instance Properties of a sub-Model
Summary: If I edit a child model, I can't set the Instance Properties. When I try to do so, and go back to edit it again, I find that they aren't there.
(Noticed by Xavier.)
Raised to Critical because the problem might be deeper: reports from Xavier suggest that editing any Property of a sub-Model may be failing.
This is actually a fairly serious design bug: we're not dealing with the fact that the Instance Properties of a sub-Model are potentially a superset of the parent. Need to think this through, and figure out a way to set them!
A good example here is the Lochleven Inventory Space. I can set the Instance Properties for Item Base, but not for Component.
(The problem might be display rather than editing. It keeps claiming that I am Saving successfully as I re-order the Properties, but when I open the Editor, they all show as Model Properties.)
