General react performance improvements (#2796)

* General React performance improvements

* Cleaned up unused props/state in PermaLinkView and PostFocusView

webapp/components/sidebar.jsx

@@ -698,8 +698,3 @@ export default class Sidebar extends React.Component {
         );
     }
 }
-
-Sidebar.defaultProps = {
-};
-Sidebar.propTypes = {
-};