Bug 160429 Drag the datasource and dataset and produce an error gradation in data explorer
Details: Drag the datasource and dataset and produce an error gradation in data explorer Step: 1.New 4 datasource named d1, d2, d3, d4. 2.Drag the datasource in data explorer to change the gradation. (1) Drag d1 between d2 and d3. (2) Drag d2 between d3 and d4. (3) Drag d4 between d2 and d3. (4) Drag d4 to the top. (5) Drag d3 between d1 and d2. (6) Drag d3 to the top. Actual result: (1) d1 will be move to bottom. (2) d2 will be move to bottom. (3) d4 will not be move to anywhere. (4) d4 will not be move to anywhere. (5) d3 will be move to bottom. (6) d3 will be move to bottom. Excepted result: The datasource will be move to the correct station.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/ModuleHandle.java
* Calls to inform a save is successful. Must be called after a successful
	 * completion of a save done using <code>serialize</code>.
	 */
	public void onSave( )
	{
		module.onSave( );
	}
	/**
	 * Removes a given validation listener. If the listener not registered, then
	 * the request is silently ignored.
	 * 
	 * @param listener
	 *            the listener to de-register
	 * @return <code>true</code> if <code>listener</code> is sucessfully
	 *         removed. Otherwise <code>false</code>.
	 */
	public boolean removeValidationListener( IValidationListener listener )
	{
		return getModule( ).removeValidationListener( listener );
	}
	/**
	 * Checks the element name in name space of this report.
	 * 
	 * <ul>
	 * <li>If the element name is required and duplicate name is found in name
	 * space, rename the element with a new unique name.
	 * <li>If the element name is not required, clear the name.
	 * </ul>
	 * 
	 * @param elementHandle