Bug 168026 Still use the existing data binding even though the aggregate is different
I had a table in which a data binding which aggregates on a group. When I insert a new data item in the report, although the expressions are same, it aggregates on All, then it refered to the existing data binding. The expected behavior would be a new data binding is created with different aggregates.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/ReportItemHandle.java
* the Presentation engine.
	 * 
	 * @param value
	 *            the script to set
	 * @throws SemanticException
	 *             if the property is locked.
	 */
	public void setOnRender( String value ) throws SemanticException
	{
		setProperty( IReportItemModel.ON_RENDER_METHOD, value );
	}
	/**
	 * Returns the iterator for parameter binding list defined on this report
	 * item. The element in the iterator is the corresponding
	 * <code>StructureHandle</code> that deal with a <code>ParamBinding</code>
	 * in the list.
	 * 
	 * @return the iterator for parameter binding structure list defined on this
	 *         data set.
	 * 
	 * @see org.eclipse.birt.report.model.api.elements.structures.ParamBinding
	 */
	public Iterator paramBindingsIterator( )
	{
		PropertyHandle propHandle = getPropertyHandle( IReportItemModel.PARAM_BINDINGS_PROP );
		assert propHandle != null;
		return propHandle.iterator( );
	}
	/**
	 * Sets a table of contents entry for this item. The TOC property defines an