Updating client dependencies. Switching to yarn. (#6433)

* Updating client dependancies. Switching to using yarn.

* Updating React

* Moving pure components to using function syntax (performance gains with newer react version)

* Updating client dependancies.

* Ignore .yarninstall

* Enabling pre-lockfile because it's the entire point of using yarn.

* Removing old webpack config

* Moving to new prop-types

* Fixing ESLint Errors

* Updating jest snapshots.

* Cleaning up package.json

webapp/components/activity_log_modal/activity_log_modal.jsx

@@ -8,16 +8,17 @@ import UserStore from 'stores/user_store.jsx';
 import * as Utils from 'utils/utils.jsx';
 
 import $ from 'jquery';
+import PropTypes from 'prop-types';
 import React from 'react';
 import {Modal} from 'react-bootstrap';
 import {FormattedMessage, FormattedTime, FormattedDate} from 'react-intl';
 
 export default class ActivityLogModal extends React.Component {
     static propTypes = {
-        onHide: React.PropTypes.func.isRequired,
-        actions: React.PropTypes.shape({
-            getSessions: React.PropTypes.func.isRequired,
-            revokeSession: React.PropTypes.func.isRequired
+        onHide: PropTypes.func.isRequired,
+        actions: PropTypes.shape({
+            getSessions: PropTypes.func.isRequired,
+            revokeSession: PropTypes.func.isRequired
         }).isRequired
     }