Bug 201368 Support "Not In" operator in filter list
Description: After we support "IN" filter we should also support the "Not In" filter. Data part has already support the "Not In" filter, so hope model can support that operator in the filter operator list. Regards!
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/command/CssCommand.java
* @throws SemanticException
	 *             if failed to remove <code>CssStyleSheet</code> strcutre
	 */
	public void dropCss( CssStyleSheet sheet ) throws SemanticException
	{
		if ( sheet == null )
		{
			return;
		}
		ActivityStack stack = getActivityStack( );
		stack.startTrans( );
		String fileName = sheet.getFileName( );
		try
		{
			removeIncludeCss( fileName );
		}
		catch ( SemanticException ex )
		{
			stack.rollback( );
			throw ex;
		}
		CssRecord record = new CssRecord( module, element, sheet, false );
		getActivityStack( ).execute( record );
		getActivityStack( ).commit( );
	}
	/**
	 * Drop one css file.
	 * 
	 * @param fileName
	 *            absolute file name of the css.