Support for Google OAuth2

Fixes #190 

Google closed registration to new OpenID 2.0 clients on May 19, 2014. This means new TraitDB servers cannot use Google OpenID. Google shuts down the OpenID 2.0 service on April 20, 2015. See https://developers.google.com/+/api/auth-migration#timetable for details.

This pull request changes Google login to use Google OAuth 2