Thank you for the PR.

The reason I waited to merge this one was due to the work I was doing for Wino Calendar. Authentication library is now abstracted into separate project called Wino.Authentication and all authenticators are moved there.

Previously, authentications were handled by the UWP app, but now since we have a separate server process, it's better to delegate all authentication to the server and completely remove authentication libraries from the UWP app. During this work, I have implemented Gmail Auth library for .NET. Got rid of the old code that UWP was using. This means refreshing token will automatically be handled by this library in the server.

Checking for expired token is also handled in the new authenticator as well using this library. Therefore, these changes makes this PR obsolete for now.