Remove use of deprecated React.PropTypes

Replace all uses of React.PropTypes with PropTypes and importing PropTypes from
'prop-types'.

src/components/structures/login/Login.js

@@ -18,6 +18,7 @@ limitations under the License.
 'use strict';
 
 import React from 'react';
+import PropTypes from 'prop-types';
 import { _t } from '../../../languageHandler';
 import * as languageHandler from '../../../languageHandler';
 import sdk from '../../../index';
@@ -36,27 +37,27 @@ module.exports = React.createClass({
     displayName: 'Login',
 
     propTypes: {
-        onLoggedIn: React.PropTypes.func.isRequired,
+        onLoggedIn: PropTypes.func.isRequired,
 
-        enableGuest: React.PropTypes.bool,
+        enableGuest: PropTypes.bool,
 
-        customHsUrl: React.PropTypes.string,
-        customIsUrl: React.PropTypes.string,
-        defaultHsUrl: React.PropTypes.string,
-        defaultIsUrl: React.PropTypes.string,
+        customHsUrl: PropTypes.string,
+        customIsUrl: PropTypes.string,
+        defaultHsUrl: PropTypes.string,
+        defaultIsUrl: PropTypes.string,
         // Secondary HS which we try to log into if the user is using
         // the default HS but login fails. Useful for migrating to a
         // different home server without confusing users.
-        fallbackHsUrl: React.PropTypes.string,
+        fallbackHsUrl: PropTypes.string,
 
-        defaultDeviceDisplayName: React.PropTypes.string,
+        defaultDeviceDisplayName: PropTypes.string,
 
         // login shouldn't know or care how registration is done.
-        onRegisterClick: React.PropTypes.func.isRequired,
+        onRegisterClick: PropTypes.func.isRequired,
 
         // login shouldn't care how password recovery is done.
-        onForgotPasswordClick: React.PropTypes.func,
-        onCancelClick: React.PropTypes.func,
+        onForgotPasswordClick: PropTypes.func,
+        onCancelClick: PropTypes.func,
     },
 
     getInitialState: function() {