Bug 188578 Add "displayColumnName" on TabularLevel
Add Property "displayColumnName" on TabbularLevel and corresponding APIs on handle. Property Type: expression.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/writer/ModuleWriter.java
*/
	public void visitFreeForm( FreeForm obj )
	{
		writer.startElement( DesignSchemaConstants.FREE_FORM_TAG );
		super.visitFreeForm( obj );
		writeContents( obj, IFreeFormModel.REPORT_ITEMS_SLOT,
				DesignSchemaConstants.REPORT_ITEMS_TAG );
		writer.endElement( );
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.design.elements.DesignVisitor#visitDataItem(org.eclipse.birt.report.model.design.elements.DataItem)
	 */
	public void visitDataItem( DataItem obj )
	{
		
		boundColumnsMgr.dealData( obj, getModule( ) );
		writer.startElement( DesignSchemaConstants.DATA_TAG );
		super.visitDataItem( obj );
		property( obj, IDataItemModel.RESULT_SET_COLUMN_PROP );
		resourceKey( obj, IDataItemModel.HELP_TEXT_KEY_PROP,
				IDataItemModel.HELP_TEXT_PROP );
		writeAction( obj, IDataItemModel.ACTION_PROP );
		writer.endElement( );
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.elements.ElementVisitor#visitMultiLineDataItem(org.eclipse.birt.report.model.elements.TextDataItem)