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
* @throws SemanticException
	 *             if the method is locked.
	 * 
	 * @see #getOnPageBreak()
	 */
	public void setOnPageBreak( String script ) throws SemanticException
	{
		setProperty( ON_PAGE_BREAK_METHOD, script );
	}
	/**
	 * Returns the bound columns that binds the data set columns. The item in
	 * the iterator is the corresponding <code>ComputedColumnHandle</code>.
	 * 
	 * @return a list containing the bound columns.
	 */
	public Iterator columnBindingsIterator( )
	{
		PropertyHandle propHandle = getPropertyHandle( BOUND_DATA_COLUMNS_PROP );
		return propHandle.iterator( );
	}
	/**
	 * Get a handle to deal with the bound column.
	 * 
	 * @return a handle to deal with the boudn data column.
	 */
	public PropertyHandle getColumnBindings( )
	{
		return getPropertyHandle( BOUND_DATA_COLUMNS_PROP );
	}
	/**