In the Model Editor, it is too easy to re-order Properties when you try to scroll

Summary: Specific to touchscreens: when you drag up or down to scroll, you often wind up rearranging the Model's Properties by accident.

(Actually reported by Xavier.)

This points out that we need some re-think of the UX in the Editor -- the problem is specific to touchscreens, but we shouldn't hack this.

Xavier suggests using grabbers for re-ordering Properties, similar to how we do with Lists. I don't love the UX of the List grabbers, but he may be correct that this is the only sensible way to square the circle.