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/PostMeta.js

@@ -0,0 +1,45 @@
+import Component from 'flarum/Component';
+import humanTime from 'flarum/helpers/humanTime';
+import fullTime from 'flarum/helpers/fullTime';
+
+/**
+ * The `PostMeta` component displays the time of a post, and when clicked, shows
+ * a dropdown containing more information about the post (number, full time,
+ * permalink).
+ *
+ * ### Props
+ *
+ * - `post`
+ */
+export default class PostMeta extends Component {
+  view() {
+    const post = this.props.post;
+    const time = post.time();
+    const permalink = window.location.origin + app.route.post(post);
+    const touch = 'ontouchstart' in document.documentElement;
+
+    // When the dropdown menu is shown, select the contents of the permalink
+    // input so that the user can quickly copy the URL.
+    const selectPermalink = function() {
+      setTimeout(() => $(this).parent().find('.permalink').select());
+
+      m.redraw.strategy('none');
+    };
+
+    return (
+      <div className="dropdown post-meta">
+        <a href="javascript:;" data-toggle="dropdown" className="dropdown-toggle" onclick={selectPermalink}>
+          {humanTime(time)}
+        </a>
+
+        <div className="dropdown-menu">
+          <span className="number">Post #{post.number()}</span>
+          {fullTime(time)}
+          {touch
+            ? <a href="btn btn-default permalink" href={permalink}>{permalink}</a>
+            : <input className="form-control permalink" value="permalink" onclick={e => e.stopPropagation()} />}
+        </div>
+      </div>
+    );
+  }
+}