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/avatars/BaseAvatar.js

@@ -2,6 +2,7 @@
 Copyright 2015, 2016 OpenMarket Ltd
 Copyright 2018 New Vector Ltd
 Copyright 2019 Michael Telatynski <7t3chguy@gmail.com>
+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.
@@ -24,7 +25,7 @@ import AvatarLogic from '../../../Avatar';
 import SettingsStore from "../../../settings/SettingsStore";
 import AccessibleButton from '../elements/AccessibleButton';
 
-module.exports = createReactClass({
+export default createReactClass({
     displayName: 'BaseAvatar',
 
     propTypes: {

src/components/views/avatars/MemberAvatar.js

@@ -1,5 +1,6 @@
 /*
 Copyright 2015, 2016 OpenMarket 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 @@ const Avatar = require('../../../Avatar');
 const sdk = require("../../../index");
 const dispatcher = require("../../../dispatcher");
 
-module.exports = createReactClass({
+export default createReactClass({
     displayName: 'MemberAvatar',
 
     propTypes: {

src/components/views/avatars/RoomAvatar.js

@@ -22,7 +22,7 @@ import Modal from '../../../Modal';
 import sdk from "../../../index";
 import Avatar from '../../../Avatar';
 
-module.exports = createReactClass({
+export default createReactClass({
     displayName: 'RoomAvatar',
 
     // Room may be left unset here, but if it is,