New live stat: Total new users today

* Add NT (Obv/2 throwback) MCI for new users today
* Keep live stat up to date in stat log
* Exposed via WFC

core/sys_event_user_log.js

@@ -3,6 +3,7 @@
 
 const Events    = require('./events.js');
 const LogNames  = require('./user_log_name.js');
+const SysProps  = require('./system_property.js');
 
 const DefaultKeepForDays = 365;
 
@@ -26,6 +27,7 @@ module.exports = function systemEventUserLogInit(statLog) {
         const detailHandler = {
             [ systemEvents.NewUser ] : (e) => {
                 append(e, LogNames.NewUser, 1);
+                statLog.incrementNonPersistentSystemStat(SysProps.NewUsersTodayCount, 1);
             },
             [ systemEvents.UserLogin ] : (e) => {
                 append(e, LogNames.Login, 1);