Massive JavaScript cleanup

- Use JSX for templates
- Docblock/comment everything
- Mostly passes ESLint (still some work to do)
- Lots of renaming, refactoring, etc.

CSS hasn't been updated yet.

js/forum/src/components/NotificationsDropdown.js

@@ -0,0 +1,44 @@
+import Component from 'flarum/Component';
+import icon from 'flarum/helpers/icon';
+import NotificationList from 'flarum/components/NotificationList';
+
+export default class NotificationsDropdown extends Component {
+  constructor(...args) {
+    super(...args);
+
+    /**
+     * Whether or not the notifications dropdown is visible.
+     *
+     * @type {Boolean}
+     */
+    this.showing = false;
+  }
+
+  view() {
+    const user = app.session.user;
+    const unread = user.unreadNotificationsCount();
+
+    return (
+      <div className="dropdown btn-group notifications-dropdown">
+        <a href="javascript:;"
+          className={'dropdown-toggle btn btn-default btn-rounded btn-naked btn-icon' + (unread ? ' unread' : '')}
+          data-toggle="dropdown"
+          onclick={this.onclick.bind(this)}>
+          <span className="notifications-icon">{unread || icon('bell')}</span>
+          <span className="label">Notifications</span>
+        </a>
+        <div className="dropdown-menu dropdown-menu-right">
+          {this.showing ? NotificationList.component() : ''}
+        </div>
+      </div>
+    );
+  }
+
+  onclick() {
+    if (app.drawer.isOpen()) {
+      m.route(app.route('notifications'));
+    } else {
+      this.showing = true;
+    }
+  }
+}