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
* The feature id for the '<em><b>Toolbar</b></em>' containment reference.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	public static final int PART__TOOLBAR = ApplicationPackageImpl.CONTRIBUTION_FEATURE_COUNT + 19;
	/**
	 * The feature id for the '<em><b>Closeable</b></em>' attribute.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	public static final int PART__CLOSEABLE = ApplicationPackageImpl.CONTRIBUTION_FEATURE_COUNT + 20;
	/**
	 * The number of structural features of the '<em>Part</em>' class.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	public static final int PART_FEATURE_COUNT = ApplicationPackageImpl.CONTRIBUTION_FEATURE_COUNT + 21;
	/**
	 * The meta object id for the '{@link org.eclipse.e4.ui.model.application.ui.basic.impl.InputPartImpl <em>Input Part</em>}' class.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @see org.eclipse.e4.ui.model.application.ui.basic.impl.InputPartImpl
	 * @see org.eclipse.e4.ui.model.application.ui.basic.impl.BasicPackageImpl#getInputPart()
	 * @generated