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 meta object literal for the '<em><b>Item Type</b></em>' attribute feature.
		 * <!-- begin-user-doc -->
		 * <!-- end-user-doc -->
		 * @generated
		 */
		EAttribute LEGEND__ITEM_TYPE = eINSTANCE.getLegend_ItemType( );
		/**
		 * The meta object literal for the '<em><b>Title</b></em>' containment reference feature.
		 * <!-- begin-user-doc -->
		 * <!-- end-user-doc -->
		 * @generated
		 */
		EReference LEGEND__TITLE = eINSTANCE.getLegend_Title( );
		/**
		 * The meta object literal for the '<em><b>Title Position</b></em>' attribute feature.
		 * <!-- begin-user-doc -->
		 * <!-- end-user-doc -->
		 * @generated
		 */
		EAttribute LEGEND__TITLE_POSITION = eINSTANCE.getLegend_TitlePosition( );
		/**
		 * The meta object literal for the '<em><b>Show Value</b></em>' attribute feature.
		 * <!-- begin-user-doc -->
		 * <!-- end-user-doc -->
		 * @generated
		 */
		EAttribute LEGEND__SHOW_VALUE = eINSTANCE.getLegend_ShowValue( );
		/**
		 * The meta object literal for the '<em><b>Show Percent</b></em>' attribute feature.
		 * <!-- begin-user-doc -->