Replacing [WebApiUrl] by the Graph URL (#165)

* Replacing [WebApiUrl] by the Graph UR
* Adding an empty Callback Path so that the redirect URI is really the one mentioned in the README.md

Author: jmprieur

2. Web API now calls Microsoft Graph/TodoListService/appsettings.json

@@ -3,6 +3,7 @@
     "Instance": "https://login.microsoftonline.com/",
     "ClientId": "[Enter_client_ID_Of_TodoListService-v2_from_Azure_Portal,_e.g._2ec40e65-ba09-4853-bcde-bcb60029e596]",
     "ClientSecret": "[Enter_client_secret_as_added_fom_the_certificates_&_secrets_page_from_your_app_registration]",
+    "CallbackPath" :  "",
 
     /*
       You need specify the TenantId only if you want to accept access tokens from a single tenant (line of business app)
@@ -20,7 +21,7 @@
           App ID URI of a legacy v1 web application
         Applications are registered in the https://portal.azure.com portal.
       */
-      "BaseUrl": "[WebApiUrl]",
+      "BaseUrl": "https://graph.microsoft.com/v1.0",
       "Scopes": "user.read"
     },
   "Kestrel": {