Bug 211703 Support muti-view on report item.
As title described.
xtab/org.eclipse.birt.report.item.crosstab.core/src/org/eclipse/birt/report/item/crosstab/core/de/CrosstabReportItemHandle.java
* @return
	 * @throws SemanticException
	 */
	public void setAggregationFunction( int axisType,
			MeasureViewHandle measureView, String function )
			throws SemanticException
	{
		new CrosstabReportItemTask( this ).setAggregationFunction( axisType,
				measureView, function );
	}
	/**
	 * Returns the view that is being used.
	 * 
	 * @return the view that is being used
	 */
	public DesignElementHandle getCurrentView( )
	{
		return new CrosstabReportItemTask( this ).getCurrentView( );
	}
	/**
	 * Adds a new element as the view.
	 * 
	 * @param viewElement
	 *            the element
	 * @throws SemanticException
	 */
	public void addView( DesignElementHandle viewElement )
			throws SemanticException
	{
		new CrosstabReportItemTask( this ).addView( viewElement );