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
* associate query with Table, List and Chart item design.
		 */
		private void registerQueryAndElement( IBaseQueryDefinition query, 
				ReportItemDesign reportItem )
		{
			assert query!=null && reportItem != null;
			if( mapQueryToReportItem == null )
			{
				mapQueryToReportItem = new HashMap( );
			}
			mapQueryToReportItem.put( query, reportItem );
		}
		
		/*
		 * (non-Javadoc)
		 * 
		 * @see org.eclipse.birt.report.engine.ir.ReportItemVisitor#visitMultiLineItem(org.eclipse.birt.report.engine.ir.MultiLineItemDesign)
		 */
		public Object visitMultiLineItem( MultiLineItemDesign multiLine,
				Object value )
		{
			BaseQueryDefinition query = prepareVisit( multiLine );
			handleReportItemExpressions( multiLine );
			addExpression( multiLine.getContent( ) );
			finishVisit( query );
			return value;
		}
		/*
		 * (non-Javadoc)
		 *