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
* @throws IOException
	 *             if the file cannot be saved
	 * 
	 * @see #save()
	 */
	public void saveAs( String newName ) throws IOException
	{
		setFileName( newName );
		save( );
	}
	/**
	 * Writes the report design to the given output stream. The caller must call
	 * <code>onSave</code> if the save succeeds.
	 * 
	 * @param out
	 *            the output stream to which the design is written.
	 * @throws IOException
	 *             if the file cannot be written to the output stream
	 *             successfully.
	 */
	public void serialize( OutputStream out ) throws IOException
	{
		assert out != null;
		module.prepareToSave( );
		module.getWriter( ).write( out );
		module.onSave( );
	}
	/**
	 * Sets the name of the author of the design report.
	 *