Remove Open ID support

[pceccato]

Google has turned off support for open id 2.0. Thanks for letting me know Google!

https://cloud.google.com/appengine/docs/deprecations/open_id

This breaks the yahoo login as implemented by simpleauth

The demo project here:

https://simpleauth.appspot.com

illustrates the issue

[x1ddos]

We should probably switch Yahoo to OAuth2: https://developer.yahoo.com/oauth2/guide/

[x1ddos]

And remove Open ID.