PanelConfiguration: move two "Add [thing]" buttons into a menu
This dialog is intended to be very narrow, yet its header has a label and two buttons, one somewhat long. In English this works out okay, but when translated into other languages, it's possible for the labels to be very long and cause the dialog to balloon in size, which looks really bad.
Instead, collapse the two buttons into a menu, which ensures there's enough space with all languages.
Edited by Nate Graham