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/admin_console/text_setting.jsx

@@ -1,3 +1,5 @@
+import PropTypes from 'prop-types';
+
 // Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
 // See License.txt for license information.
 
@@ -9,18 +11,18 @@ import Constants from 'utils/constants.jsx';
 export default class TextSetting extends React.Component {
     static get propTypes() {
         return {
-            id: React.PropTypes.string.isRequired,
-            label: React.PropTypes.node.isRequired,
-            placeholder: React.PropTypes.string,
-            helpText: React.PropTypes.node,
-            value: React.PropTypes.oneOfType([
-                React.PropTypes.string,
-                React.PropTypes.number
+            id: PropTypes.string.isRequired,
+            label: PropTypes.node.isRequired,
+            placeholder: PropTypes.string,
+            helpText: PropTypes.node,
+            value: PropTypes.oneOfType([
+                PropTypes.string,
+                PropTypes.number
             ]).isRequired,
-            maxLength: React.PropTypes.number,
-            onChange: React.PropTypes.func,
-            disabled: React.PropTypes.bool,
-            type: React.PropTypes.oneOf([
+            maxLength: PropTypes.number,
+            onChange: PropTypes.func,
+            disabled: PropTypes.bool,
+            type: PropTypes.oneOf([
                 'input',
                 'textarea'
             ])