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
* @param units
	 *            the default units for the design.
	 * @throws SemanticException
	 *             if the input unit is not one of allowed.
	 * 
	 * @see org.eclipse.birt.report.model.api.metadata.DimensionValue
	 */
	public void setDefaultUnits( String units ) throws SemanticException
	{
		setStringProperty( UNITS_PROP, units );
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.api.DesignElementHandle#getElement()
	 */
	public DesignElement getElement( )
	{
		return module;
	}
	/**
	 * Finds the handle to an element by a given element ID. Returns
	 * <code>null</code> if the ID is not valid, or if this session does not
	 * use IDs.
	 * 
	 * @param id
	 *            ID of the element to find
	 * @return A handle to the element, or <code>null</code> if the element
	 *         was not found or this session does not use IDs.
	 */