Bug 183919 [Enhancement] add a switch to determine whether to clean viewer image folder when session expires
in current viewer implementation, file in image folder is deleted when its corresponding session expires, could viewer add a switch to allow users to decide whether this deletion operation should be performed.
viewer/org.eclipse.birt.report.viewer/birt/WEB-INF/classes/org/eclipse/birt/report/listener/ViewerHttpSessionListener.java
/*************************************************************************************
 * Copyright (c) 2004 Actuate Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     Actuate Corporation - Initial implementation.
 ************************************************************************************/
package org.eclipse.birt.report.listener;
import java.util.HashMap;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
import org.eclipse.birt.report.IBirtConstants;
import org.eclipse.birt.report.utility.ParameterAccessor;
/**
 * HttpSession Listener for BIRT viewer web application. Do some necessary jobs
 * when create a new HttpSession or destroy it.
 * <p>
 */
public class ViewerHttpSessionListener implements HttpSessionListener