Bug 755412 - [UOA] Update OAuth flow according to Google documentation

While the existing parameters continue to work, Google is no longer
granting us a refresh token (which could be used to short-cut the
authentication and avoid loading a web view).
By following the latest documentation at

 https://developers.google.com/identity/protocols/OAuth2InstalledApp

we change the application type to "Installed application" (this gives us
an additional pair of keys) and set the callback URI to
https://localhost/.