Bug 120503 Cascading Parameter can not drop into layout
Details: Cascading Parameter can not drop into layout Step: 1.Open a report design and Create a Sample Data Source and data set by "select * from CLASSICMODELS.CUSTOMERS" 2.New a cascading parameter and create CUSTOMERSNUMBER and CUSTOMERSNAME in parameter named number and name. Press OK 3.Drop parameter name into layout. Actual results: The parameter in Cascading Parameter Group can not drop to layout
UI/org.eclipse.birt.report.designer.core/src/org/eclipse/birt/report/designer/util/DEUtil.java
* Relativizes the path against this base path.
	 * 
	 * @param basePath
	 *            the base path
	 * @param path
	 *            the path to convert
	 * @return The relative path based on the base path if it is possible, or
	 *         the original path
	 * 
	 */
	public static String getRelativedPath( String basePath, String path )
	{
		
		
		return URIUtil.getRelativePath( new File( basePath ).getParent( ),
				new File( path ).getParent( ) )
				+ "/" + new File( path ).getName( );
	}
	/**
	 * Returns the handle of the action of the given element.
	 * 
	 * @param element
	 *            the element handle
	 * @return the handle of the action, or null if the element is not a proper
	 *         type
	 */
	public static ActionHandle getActionHandle( ReportItemHandle element )
	{
		ActionHandle actionHandle = null;
		if ( element instanceof LabelHandle )