Bug 212497 Need api to get all referencable report item with cube
Need model provide new api to return all referencable report items for dataset or cube respectively. For instance: getAvailableDataSetBindingReferenceList(); getAvailableCubeBindingReferenceList(); also keep current api: getAvailableDataBindingReferenceList().
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/ReportItemHandle.java
* <li>DATABINDING_TYPE_NONE, no data binding.
	 * <li>DATABINDING_TYPE_DATA, data binding to data set or cube.
	 * <li>DATABINDING_TYPE_REPORT_ITEM_REF, data binding to another report
	 * item.
	 * </ul>
	 * 
	 * @return the data binding type of this report item
	 */
	public int getDataBindingType( )
	{
		if ( getDataBindingReferenceName( ) != null )
			return DATABINDING_TYPE_REPORT_ITEM_REF;
		
		
		if ( getDataSet( ) != null ||
				element.getProperty( module, "cube" ) != null ) 
			return DATABINDING_TYPE_DATA;
		return DATABINDING_TYPE_NONE;
	}
	/**
	 * Returns report items that can be referred by other report items by data
	 * binding reference property.
	 * <p>
	 * Two kinds of report items can be referred:
	 * <ul>
	 * <li>The report item has dataset property defined. That is, data set
	 * property is set locally and databinding ref property is null.
	 * <li>The report item has data binding reference to other report items.
	 * </ul>
	 * ReportItem in the design are all applicable. Each entry of the return