Changed autodetection of SiteURL (#3764)

* Changed autoconfiguration of SiteURL to be done on every request

* Added SiteURL to system console

webapp/utils/utils.jsx

@@ -1338,3 +1338,7 @@ export function isValidPassword(password) {
 
     return errorMsg;
 }
+
+export function getSiteURL() {
+    return global.mm_config.SiteURL || window.location.origin;
+}