rename helpers -> dateUtils and add header

Signed-off-by: Adam Warner <me@adamwarner.co.uk>

src/components/log/LiveLog.tsx

@@ -11,7 +11,7 @@
 import React, { Component } from "react";
 import { animateScroll } from "react-scroll";
 import { WithAPIData } from "../common/WithAPIData";
-import { humanTimestamp } from "../../util/helpers";
+import { humanTimestamp } from "../../util/dateUtils";
 import api from "../../util/api";
 
 export interface LiveLogProps {

src/util/dateUtils.tsx

@@ -1,3 +1,13 @@
+/* Pi-hole: A black hole for Internet advertisements
+ * (c) 2019 Pi-hole, LLC (https://pi-hole.net)
+ * Network-wide ad blocking via your own hardware.
+ *
+ * Web Interface
+ * Date/Time utility functions
+ *
+ * This file is copyright under the latest version of the EUPL.
+ * Please see LICENSE file for your rights under this license. */
+
 export function humanTimestamp(input: number) {
   var date = new Date(input * 1000);
   var hours = date.getHours();