Need the ability to add arbitrary components to groups. This is really intended
to support arbitrary components in toolbars without having to fudge around by
nesting the gui command toolbar in the 'real' toolbar.
Will need to consider how the group and the application can access the new
component. For example, if the applicaiton creates the component, the group
needs an elegant way to get it (preferably without relying on static methods),
ie through a component factory or something similar.
Component createComponent(String id);
To make this consistent, I should consider using the same mechanism for icons as