Bug 122854 There is redundant columns in "available columns" list in "export data" dialog.
Description: There is redundant columns in "available columns" list in "export data" dialog. Steps to reproduce: 1. Preview attached design in web viewer. 2. Select the table and click on "export" button. 3. There is a "detail" column name in "available columns" list which is not data set column.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/data/dte/ReportQueryBuilder.java
* @see org.eclipse.birt.report.engine.ir.ReportItemVisitor#visitFreeFormItem(org.eclipse.birt.report.engine.ir.FreeFormItemDesign)
		 */
		public Object visitFreeFormItem( FreeFormItemDesign container,
				Object value )
		{
			BaseQueryDefinition query = prepareVisit( container );
			handleReportItemExpressions( container );
			for ( int i = 0; i < container.getItemCount( ); i++ )
				container.getItem( i ).accept( this, value );
			finishVisit( query );
			return value;
		}
		/*
		 * (non-Javadoc)
		 * 
		 * @see org.eclipse.birt.report.engine.ir.ReportItemVisitor#visitGridItem(org.eclipse.birt.report.engine.ir.GridItemDesign)
		 */
		public Object visitGridItem( GridItemDesign grid, Object value )
		{
			BaseQueryDefinition query = prepareVisit( grid );
			handleReportItemExpressions( grid );
			for ( int i = 0; i < grid.getColumnCount( ); i++ )
			{
				
				
			}
			for ( int i = 0; i < grid.getRowCount( ); i++ )
				handleRow( grid.getRow( i ), value );
			finishVisit( query );
			return value;