I should be able to disable the "Create a *Foo*" in Link selectors

Summary: The problem here is most apparent when tabbing through the Create a Issue Editor page. You hit space to edit the Issue Priority, and then try to use arrows to go through the options, but when you hit "Create a New Priority", it kicks you into the creation window, which is totally not what you want.

In general, the "Create" option often shouldn't be legal on these Links. We really should have a concept of "sealed" -- a Property you can set on the Model, which says that you can't Create new Instances from the Editor like that, but only be hand-creating new ones.