In the Property Editor, the Done button should be in the tab order

Summary: Both when creating and editing a Property, the Done is not currently in the tab order, and that's a hassle.

The cause appears fairly straightforward -- it clearly has to do with the dynamic nature of the page, and the way that we're inserting the Property Editor into it. In particular, I would bet that having the sub-editor's controls loading after we build the Done button is confusing things a bit.

But fixing this isn't at all obvious. It looks to me like the right answer is a global one: adding a general concept of tabindex, and a responsibility for the various parts of the page to set up their tabindexes explicitly, with a "reindex" function that goes through and redoes it.

That said, I may be able to constrain it with some rules of thumb for now, at least constraining it to the Editor, and using global hardcoded solutions for the rest.