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
writer.endElement( );
	}
	/**
	 * Writes the columns slot of <code>GridItem</code> and
	 * <code>TableItem</code>.
	 * 
	 * @param obj
	 *            the grid item or table item
	 * @param slot
	 *            the columns slot
	 */
	private void writeColumns( DesignElement obj, int slot )
	{
		assert obj instanceof GridItem || obj instanceof TableItem;
		assert slot == IGridItemModel.COLUMN_SLOT
				|| slot == ITableItemModel.COLUMN_SLOT;
		
		
		
		boolean revert = true;
		if ( revert )
		{
			writeContents( obj, slot, null );
			return;
		}
		List list = obj.getSlot( slot ).getContents( );
		if ( list.isEmpty( ) )
			return;
		
		boolean needWrite = false;