(TK-92) Add graceful-shutdown support

Add graceful-shutdown support to the Jetty9 Webservice. Now,
when the webserver is shutdown, the server will give open
requests a chance to resolve themselves. Allow user to
configure the graceful shutdown stop timeout.
+1.  I think we end up with the same behavior since the timeout of 0 would terminate immediately but I agree there's no need to add the StatisticsHandler into the stack if we aren't doing a graceful shutdown.  Good catch.