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/utility/ParameterAccessor.java
*/
	public static boolean isWorkingFolderAccessOnly( )
	{
		return isWorkingFolderAccessOnly;
	}
	/**
	 * if display text of select parameter
	 * 
	 * @param paramName
	 * @return
	 */
	public static String isDisplayText( String paramName )
	{
		if ( paramName == null )
			return null;
		if ( paramName.startsWith( PREFIX_DISPLAY_TEXT ) )
		{
			return paramName.replaceFirst( PREFIX_DISPLAY_TEXT, "" ); 
		}
		return null;
	}
	/**
	 * Generates a file name for output attachment.
	 * 
	 * @param request
	 * @param format
	 * @return the file name
	 */
	public static String generateFileName( HttpServletRequest request,
			String format )