Frontent dev env (#247)

* Added frontend development files/environment

* More items-categories related removals

* Improvements in pages templates (inc. static pages)

* Improvements in video player

* Added empty home page message + cta

* Updates in media, playlist and management pages

* Improvements in material icons font loading

* Replaced media & playlists links in frontend dev-env

* frontend package version update

* chnaged frontend dev url port

* static files update

* Changed default position of theme switcher

* enabled frontend docker container

frontend/src/static/js/components/media-page/ViewerError.js

@@ -0,0 +1,23 @@
+import React from 'react';
+import { MediaPageStore } from '../../utils/stores/';
+
+export default class ViewerError extends React.PureComponent {
+  render() {
+    return (
+      <div className="viewer-container" key="viewer-container-error">
+        <div className="player-container player-container-error">
+          <div className="player-container-inner">
+            <div className="error-container">
+              <div className="error-container-inner">
+                <span className="icon-wrap">
+                  <i className="material-icons">error_outline</i>
+                </span>
+                <span className="msg-wrap">{MediaPageStore.get('media-load-error-message')}</span>
+              </div>
+            </div>
+          </div>
+        </div>
+      </div>
+    );
+  }
+}