Add email notification on Two Factor recovery use (#625)

* Add email notification on Two Factor recovery use

* A user who has lost their 2fa device can clear out the
  2fa settings using a recovery code.  When this happens
  it gets logged but no notification to the user occurs.
* Add a notification to be sent when 2fa recovery code is
  used

* Add email message templates

src/Core/Services/NoopImplementations/NoopMailService.cs

@@ -87,5 +87,10 @@ namespace Bit.Core.Services
         {
             return Task.FromResult(0);
         }
+
+        public Task SendRecoverTwoFactorEmail(string email, DateTime timestamp, string ip)
+        {
+            return Task.FromResult(0);
+        }
     }
 }