added automatic client page reload (#3188)

solution for #3105 

~~not sure if updatenotification is the right place, so opinions?~~

now impleneted in `main.js`

js/server_functions.js

@@ -1,6 +1,7 @@
 const fs = require("fs");
 const path = require("path");
 const Log = require("logger");
+const startUp = new Date();
 
 /**
  * Gets the config.
@@ -11,6 +12,15 @@ function getConfig(req, res) {
 	res.send(config);
 }
 
+/**
+ * Gets the startup time.
+ * @param {Request} req - the request
+ * @param {Response} res - the result
+ */
+function getStartup(req, res) {
+	res.send(startUp);
+}
+
 /**
  * A method that forwards HTTP Get-methods to the internet to avoid CORS-errors.
  *
@@ -117,4 +127,4 @@ function getVersion(req, res) {
 	res.send(global.version);
 }
 
-module.exports = { cors, getConfig, getHtml, getVersion };
+module.exports = { cors, getConfig, getHtml, getVersion, getStartup };