Issue 463: Provide a signout\logout method

Src/GoogleApis.Auth.WP/OAuth2/AuthorizationCodeBroker.cs

 /*
 Copyright 2013 Google Inc
 
 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.
 */
 
 using System;
 using System.Threading;
 using System.Threading.Tasks;
 using System.Windows;
 using System.Windows.Controls;
 using Microsoft.Phone.Controls;
 
 using Google.Apis.Auth.OAuth2.Requests;
 using Google.Apis.Auth.OAuth2.Responses;
 
 namespace Google.Apis.Auth.OAuth2
 {
 /// <summary>
- /// OAuth 2.0 verification code receiver for WP that opens an embedded Googl
 e account form to enter the user's
- /// credentials and accepts the application access to its token.
+ /// OAuth 2.0 verification code receiver for Windows Phone that opens an emb
 edded Google account form to enter the
+ /// user's credentials and accepts the application access to its token.
 /// </summary>
 public class AuthorizationCodeBroker : ICodeReceiver
 {
 #region ICodeReceiver Members
 
 public string RedirectUri
 {
 get { return GoogleAuthConsts.LocalhostRedirectUri; }
 }
 
@@ skipping 39 matching lines @@
 finally
 {
 // Change back to the old layout.
 webAuthControl.Visibility = Visibility.Collapsed;
 oauthLayout.Children.Remove(webAuthControl);
 rootPage.Content = currentLayout;
 }
 }
 }
 }