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/src/org/eclipse/e4/ui/model/application/ui/basic/MBasicFactory.java
/**
	 * The singleton instance of the factory.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 */
	MBasicFactory INSTANCE = org.eclipse.e4.ui.model.application.ui.basic.impl.BasicFactoryImpl.eINSTANCE;
	/**
	 * Returns a new object of class '<em>Part</em>'.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @return a new object of class '<em>Part</em>'.
	 * @generated