I should be able to specify the display order of Choices

(User Story, Closed -> Fixed, Priority: High, Test Status: No automated tests yet , Reported By Justin du Coeur, )
Editor
Summary: This isn't strictly limited to Is a Choice Properties, but is mainly for them. The Model should have a List Property which, if given, specifies the display order of this Choice.
If there are Instances that don't appear in this list, what should we do with them? Should they be omitted, or placed at the bottom of the list?
Normally, the default should be the first item in the list. Do we need a separate Property specifying the default?