Bug 136270 Group's data binding column can only be used by the group itself
If you add some data binding columns to a group, these columns can only be used by this group itself. It should has a way to make the child can use the parent group's data binding column.
UI/org.eclipse.birt.report.designer.core/src/org/eclipse/birt/report/designer/util/DEUtil.java
* @param child
	 * @return slot id
	 */
	public static int getSlotID( Object parent, Object child )
	{
		assert parent instanceof DesignElementHandle;
		int slotID = -1;
		if ( child != null )
		{
			slotID = findSlotID( parent, child );
		}
		else
		{
			slotID = getDefaultSlotID( parent );
		}
		return slotID;
	}
	/**
	 * Find the position of the element. If the element is null, the position is
	 * last
	 * 
	 * @param parent
	 * @param element
	 * @return position
	 */
	public static int findInsertPosition( DesignElementHandle parent,
			DesignElementHandle element )
	{
		
		if ( element == null )