modernise the sample configuration file

nmdc-webfrontend.conf.SAMPLE

@@ -12,9 +12,8 @@
 	},
 	
 	"hub": {
-		"address": "127.0.0.1",
-		"port": 411,
+		"address": "nmdc://127.0.0.1:411",
 		"tag": "nmdc-webfrontend"
 	}
 	
-}
+}