Return a JSON response for all 404s.

When an endpoint did not exist, the default expressjs response
was being returned, which is text/html.

lib/www/server/api/index.js

@@ -360,6 +360,10 @@ app.use(function (err, req, res, next) {
 	}
 });
 
+app.get("*", (req, res, next) => {
+	res.status(404).send({status: 404, message: "This endpoint does not exist"});
+});
+
 app.disable('x-powered-by');
 app.enable('trust proxy');
 INFO('trust proxy is ' + (app.get('trust proxy')? 'on' : 'off'));