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/impl/BasicPackageImpl.java
* <!-- end-user-doc -->
	 * @return the meta object for class '<em>Trimmed Window</em>'.
	 * @see org.eclipse.e4.ui.model.application.ui.basic.MTrimmedWindow
	 * @generated
	 */
	public EClass getTrimmedWindow() {
		return trimmedWindowEClass;
	}
	/**
	 * Returns the meta object for the containment reference list '{@link org.eclipse.e4.ui.model.application.ui.basic.MTrimmedWindow#getTrimBars <em>Trim Bars</em>}'.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @return the meta object for the containment reference list '<em>Trim Bars</em>'.
	 * @see org.eclipse.e4.ui.model.application.ui.basic.MTrimmedWindow#getTrimBars()
	 * @see #getTrimmedWindow()
	 * @generated
	 */
	public EReference getTrimmedWindow_TrimBars() {
		return (EReference)trimmedWindowEClass.getEStructuralFeatures().get(0);
	}
	/**
	 * Returns the meta object for class '{@link org.eclipse.e4.ui.model.application.ui.basic.MTrimElement <em>Trim Element</em>}'.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @return the meta object for class '<em>Trim Element</em>'.
	 * @see org.eclipse.e4.ui.model.application.ui.basic.MTrimElement
	 * @generated
	 */
	public EClass getTrimElement() {
		return trimElementEClass;