Add Option tray now uses generic component

To test this, just click on the Add Option header link on the Config page. Should work as before.

Closes COUCHDB-2453
Hey @garrensmith, thanks! That looks promising, but I don't quite follow... When you say passing that value on standard construction, do you mean whatever code is instantiating the Tray instance (e.g. `Views.AddConfigOptionsButton`)? Since the selector is particular to that particular View, I wouldn't want whatever code is instantiating it to have to know about it to pass it along with the Views.AddConfigOptionsButton instantiation, you know? 

I'll cc @robertkowalski on this because we were chatting about it too. :)