Rename LoginBox to AuthButtons

This component displays login and register buttons. It's currently used in the
composer when viewing a room as a guest.

The name is confusing because the login flow uses are very similarly named
`mx_Login_box` as a wrapping around forms, which is totally different than these
buttons.

Additionally, the components is moved to `views/auth` since it is very simple
and auth related.

src/components/structures/LoginBox.js

@@ -1,57 +0,0 @@
-/*
-Copyright 2017 Vector Creations Ltd
-Copyright 2018 New Vector Ltd
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
-'use strict';
-
-const React = require('react');
-import { _t } from '../../languageHandler';
-const dis = require('../../dispatcher');
-const AccessibleButton = require('../../components/views/elements/AccessibleButton');
-
-module.exports = React.createClass({
-    displayName: 'LoginBox',
-
-    propTypes: {
-    },
-
-    onLoginClick: function() {
-        dis.dispatch({ action: 'start_login' });
-    },
-
-    onRegisterClick: function() {
-        dis.dispatch({ action: 'start_registration' });
-    },
-
-    render: function() {
-        const loginButton = (
-            <div className="mx_LoginBox_loginButton_wrapper">
-                <AccessibleButton className="mx_LoginBox_loginButton" element="button" onClick={this.onLoginClick}>
-                    { _t("Login") }
-                </AccessibleButton>
-                <AccessibleButton className="mx_LoginBox_registerButton" element="button" onClick={this.onRegisterClick}>
-                    { _t("Register") }
-                </AccessibleButton>
-            </div>
-        );
-
-        return (
-            <div className="mx_LoginBox">
-                { loginButton }
-            </div>
-        );
-    },
-});

src/components/structures/RoomView.js

@@ -1757,8 +1757,8 @@ module.exports = React.createClass({
         }
 
         if (MatrixClientPeg.get().isGuest()) {
-            const LoginBox = sdk.getComponent('structures.LoginBox');
-            messageComposer = <LoginBox />;
+            const AuthButtons = sdk.getComponent('views.auth.AuthButtons');
+            messageComposer = <AuthButtons />;
         }
 
         // TODO: Why aren't we storing the term/scope/count in this format