Bug 207268 Add visibility option for plot within axes
For chart with axes, we should make plot within axes invisible. Meantime, other plots, such as axes, legend and title, should be visible. This enhancement doesn't include UI change, and it is required for cross tab integration.
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/model/layout/LayoutPackage.java
* The feature id for the '<em><b>Triggers</b></em>' containment reference list.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	int LABEL_BLOCK__TRIGGERS = BLOCK__TRIGGERS;
	/**
	 * The feature id for the '<em><b>Width Hint</b></em>' attribute.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	int LABEL_BLOCK__WIDTH_HINT = BLOCK__WIDTH_HINT;
	/**
	 * The feature id for the '<em><b>Height Hint</b></em>' attribute.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	int LABEL_BLOCK__HEIGHT_HINT = BLOCK__HEIGHT_HINT;
	/**
	 * The feature id for the '<em><b>Label</b></em>' containment reference.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	int LABEL_BLOCK__LABEL = BLOCK_FEATURE_COUNT + 0;
	/**