redirect-based oauth2 flow

- authorize after redirect
    - Use localStorage to save userState before redirecting to Google OAuth2
    - put gapi mock to repo gapi-mock
    - Redirect-based google oauth 2 auth
    - works with gapi-mock
    - move fixture data to gapi-mock repo
    - remove observer on gapi fake db as the responsibility of persistance is
    now shifted to gapi-mock
    - make rv-gapi-mock a dev-only dependency
    - - Also force Google Account Chooser