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
{
			return IReportElementConstants.PARAMETER_PREFIX
					+ "[\"" + escape( ( (ParameterHandle) model ).getQualifiedName( ) ) + "\"]"; 
		}
		if ( model instanceof DataSetItemModel )
		{
			String colName = ( (DataSetItemModel) model ).getAlias( );
			if ( colName == null || colName.trim( ).length( ) == 0 )
			{
				colName = ( (DataSetItemModel) model ).getName( );
			}
			return getColumnExpression( colName );
		}
		if ( model instanceof ComputedColumnHandle )
		{
			return getColumnExpression( ( (ComputedColumnHandle) model ).getName( ) );
		}
		if ( model instanceof ResultSetColumnHandle )
		{
			return getResultSetColumnExpression( ( (ResultSetColumnHandle) model ).getColumnName( ) );
		}
		return null;
	}
	/**
	 * Returns the integer font size for string value.
	 * 
	 * @param fontSize
	 * @return
	 */
	public static int getFontSize( String fontSize )