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/SessionDropdown.js

@@ -0,0 +1,90 @@
+import avatar from 'flarum/helpers/avatar';
+import username from 'flarum/helpers/username';
+import Dropdown from 'flarum/components/Dropdown';
+import Button from 'flarum/components/Button';
+import ItemList from 'flarum/utils/ItemList';
+import Separator from 'flarum/components/Separator';
+import Group from 'flarum/models/Group';
+
+/**
+ * The `SessionDropdown` component shows a button with the current user's
+ * avatar/name, with a dropdown of session controls.
+ */
+export default class SessionDropdown extends Dropdown {
+  static initProps(props) {
+    super.initProps(props);
+
+    props.buttonClassName = 'btn btn-default btn-naked btn-rounded btn-user';
+    props.menuClassName = 'dropdown-menu-right';
+  }
+
+  view() {
+    this.props.children = this.items().toArray();
+
+    return super.view();
+  }
+
+  getButtonContent() {
+    const user = app.session.user;
+
+    return [
+      avatar(user), ' ',
+      <span className="label">{username(user)}</span>
+    ];
+  }
+
+  /**
+   * Build an item list for the contents of the dropdown menu.
+   *
+   * @return {ItemList}
+   */
+  items() {
+    const items = new ItemList();
+    const user = app.session.user;
+
+    items.add('profile',
+      Button.component({
+        icon: 'user',
+        children: 'Profile',
+        href: app.route.user(user),
+        config: m.route
+      }),
+      100
+    );
+
+    items.add('settings',
+      Button.component({
+        icon: 'cog',
+        children: 'Settings',
+        href: app.route('settings'),
+        config: m.route
+      }),
+      50
+    );
+
+    if (user.groups().some(group => Number(group.id()) === Group.ADMINISTRATOR_ID)) {
+      items.add('administration',
+        Button.component({
+          icon: 'wrench',
+          children: 'Administration',
+          href: app.forum.attribute('baseUrl') + '/admin',
+          target: '_blank'
+        }),
+        0
+      );
+    }
+
+    items.add('separator', Separator.component(), -90);
+
+    items.add('logOut',
+      Button.component({
+        icon: 'sign-out',
+        children: 'Log Out',
+        onclick: app.session.logout.bind(app.session)
+      }),
+      -100
+    );
+
+    return items;
+  }
+}