Default Style|Client: Added an on/off toggle graphic
Refactor|Client|GuiWidget: Anyone can request a geometry update
Fixed|Client|UI|LabelWidget: Incorrect layout

Omit gap between text and image if both are not present.
Client|UI|PopupWidget|PopupMenuWidget: Adding custom widgets to menu
UI|Client|ButtonWidget: Adjusted button down state scaling
UI|Client|ToggleWidget: Added ToggleWidget

A simple on/off toggle based on a button. The on/off graphic from the
style is stored centrally by GuiRootWidget.

Uses a procedural image to draw the state of the toggle.