Bug 177504 Engine doesn't provide SubQuery for extended item
Engine doesn't provide SubQuery for extended item, so chart can't use container's binding to execute the query. If possible, engine could provide an option for extended item to choose whether engine could create the query, so extended item won't create SubQuery by itself.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/extension/internal/ExtensionManager.java
public final static String EXTENSION_POINT_GENERATION = "org.eclipse.birt.report.engine.reportitemGeneration"; 
	public final static String EXTENSION_POINT_PRESENTATION = "org.eclipse.birt.report.engine.reportitemPresentation"; 
	public final static String EXTENSION_POINT_QUERY = "org.eclipse.birt.report.engine.reportitemQuery"; 
	
	/**
	 * the singleton isntance
	 */
	static protected ExtensionManager sm_instance;
	
	/**
	 * stores references to all the generation extensions
	 */
	protected HashMap generationExtensions = new HashMap();
	
	/**
	 * stores references to all the presentation extensions
	 */
	protected HashMap presentationExtensions = new HashMap();
	
	/**
	 * reference to all the query extesions.
	 */
	protected HashMap queryExtensions = new HashMap();
	
	/**
	 * stores all the emitter extensions 
	 */
	protected ArrayList emitterExtensions = new ArrayList();
	
	/**