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/PostEdited.js

@@ -0,0 +1,29 @@
+import Component from 'flarum/Component';
+import icon from 'flarum/helpers/icon';
+import humanTime from 'flarum/utils/humanTime';
+
+/**
+ * The `PostEdited` component displays information about when and by whom a post
+ * was edited.
+ *
+ * ### Props
+ *
+ * - `post`
+ */
+export default class PostEdited extends Component {
+  view() {
+    const post = this.props.post;
+    const editUser = post.editUser();
+    const title = 'Edited ' + (editUser ? 'by ' + editUser.username() + ' ' : '') + humanTime(post.editTime());
+
+    return (
+      <span className="post-edited" title={title}>{icon('pencil')}</span>
+    );
+  }
+
+  config(isInitialized) {
+    if (isInitialized) return;
+
+    this.$().tooltip();
+  }
+}