Link to related theme items in theme editor

[skeddles]

Some theme items rely on other theme items, but it's not always clear which ones.

For example, if you want to change the background color for the panel that opens when you click a ColorPickerButton, you can't do it from the ColorPickerButton, you have to adjust it on PopupPanel.

There's nothing in the interface that mentions this connection, and without knowing about all the different Control types, it's hard to know where to look. Even the docs aren't super clear about it, I would expect them to list the components that make up the control.

What I would do is add a tab to the theme editor that lists the subcomponents for the selected component. Perhaps it should also allow you to override them for just this component (maybe I want the PopupPanel for the ColorPickerButtonto look different thatn the other PopupPanels)