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
}
			else
			{
				
				return false;
			}
		}
		return true;
	}
	/**
	 * Generate document name according to report name.
	 * 
	 * @param request
	 * @return document name.
	 */
	protected static String generateDocumentFromReport(
			HttpServletRequest request )
	{
		String fileName = getReport( request, null );
		if ( fileName.indexOf( '.' ) >= 0 )
		{
			fileName = fileName.substring( 0, fileName.lastIndexOf( '.' ) );
		}
		
		String id = getParameter( request, PARAM_ID );
		if ( id != null && id.length( ) > 0 )
		{
			fileName = fileName + id + SUFFIX_REPORT_DOCUMENT;
		}
		else