Add modal look to authentication flows

This changes the auth screens to use the modal-like style of the redesign.

This does not attempt to style the actual body content of each screen.  Instead,
it covers the header area with logo, footer links, and overall modal container
only.

src/components/structures/auth/Login.js

@@ -517,7 +517,7 @@ module.exports = React.createClass({
         const Loader = sdk.getComponent("elements.Spinner");
         const AuthPage = sdk.getComponent("auth.AuthPage");
         const AuthHeader = sdk.getComponent("auth.AuthHeader");
-        const AuthFooter = sdk.getComponent("auth.AuthFooter");
+        const AuthBody = sdk.getComponent("auth.AuthBody");
         const ServerConfig = sdk.getComponent("auth.ServerConfig");
         const loader = this.state.busy ? <div className="mx_Login_loader"><Loader /></div> : null;
 
@@ -560,7 +560,7 @@ module.exports = React.createClass({
         return (
             <AuthPage>
                 <AuthHeader />
-                <div>
+                <AuthBody>
                     { header }
                     { errorTextSection }
                     { this.componentForStep(this.state.currentFlow) }
@@ -570,8 +570,7 @@ module.exports = React.createClass({
                     </a>
                     { loginAsGuestJsx }
                     <LanguageSelector />
-                    <AuthFooter />
-                </div>
+                </AuthBody>
             </AuthPage>
         );
     },