Need a way to declare a dynamic version of Display Name

Summary: I'm hitting this a lot as I implement Use Cases -- we have "child" Things such as Reconstruction (in Cooks Guild) or Project (in Gallery). They delete their "name" in a programmatic way.

Note that this can't mean making Display Name a QL field -- it's just too central to the entire world, and we can't afford to process it. But we probably can and should have a higher-level concept that sits on top of it, which is what actually gets displayed. This is in all sorts of places like offered links in the Editor, the display for a Link, etc. This field should default to Display Name, but should be an overrideable arbitrary bit of QL. Note that we often need to not only delegate it to a linked Thing, we will sometimes (as in Reconstruction) need a kicker field to disambiguate.