Bug 317417 [Model] StackElement should be abstract and interface
StackElement is only a marker for improved containment hierarchies. We should at least make it abstract but also as an interface like WindowElement, ...
bundles/org.eclipse.e4.ui.model.workbench.edit/src/org/eclipse/e4/ui/model/application/ui/basic/provider/BasicItemProviderAdapterFactory.java
* <!-- end-user-doc -->
	 * @generated
	 */
	@Override
	public Adapter createPartStackAdapter() {
		if (partStackItemProvider == null) {
			partStackItemProvider = new PartStackItemProvider(this);
		}
		return partStackItemProvider;
	}
	/**
	 * This keeps track of the one adapter used for all {@link org.eclipse.e4.ui.model.application.ui.basic.MPartSashContainer} instances.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 */
	protected PartSashContainerItemProvider partSashContainerItemProvider;
	/**
	 * This creates an adapter for a {@link org.eclipse.e4.ui.model.application.ui.basic.MPartSashContainer}.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 */
	@Override
	public Adapter createPartSashContainerAdapter() {
		if (partSashContainerItemProvider == null) {
			partSashContainerItemProvider = new PartSashContainerItemProvider(this);
		}
		return partSashContainerItemProvider;
	}