Convert CommonJS exports to ES6-compatible exports

We use `export default` begrudgingly here. Ideally we'd use just `export`, though this entire SDK expects things to be exported as a default. Instead of breaking everything, we'll sacrifice our export pattern for a smaller diff - a later commit can always do the default export -> regular export conversion.

src/components/views/settings/ChangeAvatar.js

@@ -21,7 +21,7 @@ import MatrixClientPeg from "../../../MatrixClientPeg";
 import sdk from '../../../index';
 import { _t } from '../../../languageHandler';
 
-module.exports = createReactClass({
+export default createReactClass({
     displayName: 'ChangeAvatar',
     propTypes: {
         initialAvatarUrl: PropTypes.string,

src/components/views/settings/ChangeDisplayName.js

@@ -1,6 +1,7 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -21,7 +22,7 @@ import sdk from '../../../index';
 import MatrixClientPeg from '../../../MatrixClientPeg';
 import { _t } from '../../../languageHandler';
 
-module.exports = createReactClass({
+export default createReactClass({
     displayName: 'ChangeDisplayName',
 
     _getDisplayName: async function() {

src/components/views/settings/ChangePassword.js

@@ -30,7 +30,7 @@ import { _t } from '../../../languageHandler';
 
 import sessionStore from '../../../stores/SessionStore';
 
-module.exports = createReactClass({
+export default createReactClass({
     displayName: 'ChangePassword',
 
     propTypes: {

src/components/views/settings/EnableNotificationsButton.js

@@ -20,7 +20,7 @@ import Notifier from "../../../Notifier";
 import dis from "../../../dispatcher";
 import { _t } from '../../../languageHandler';
 
-module.exports = createReactClass({
+export default createReactClass({
     displayName: 'EnableNotificationsButton',
 
     componentDidMount: function() {

src/components/views/settings/Notifications.js

@@ -63,7 +63,7 @@ function portLegacyActions(actions) {
     }
 }
 
-module.exports = createReactClass({
+export default createReactClass({
     displayName: 'Notifications',
 
     phases: {