Replace deprecated oauth2client with Google OAuth Library

[dgrieser]

This is another attempt to remove the 7 day limit.
See: #634

Thanks to hramrach and his PR #677.

Changes

1. oauth2client was completely replaced by google_auth_oauthlib
2. By default, no browser is opened, but a local webserver will be started and must be accessible by a browser
3. Options removed since they were part of oauth2client:
   • --noauth_local_webserver
   • --auth_host_name AUTH_HOST_NAME
   • --auth_host_port [AUTH_HOST_PORT [AUTH_HOST_PORT ...]]
   • --logging_level

For security reasons Google removed the run_console() strategy from their Google OAuth library.
Currently there is no feasable way to not run a local web server using this library.
See: googleapis/google-auth-library-python-oauthlib@1391486

Workaround for headless systems

If you run gcalcli on a headless linux system, you can use a SSH tunnel to make the local web server, started by the OAuth flow, accessible:

ssh -L 8080:localhost:8080 <host>

[dbarnett]

I tried this out locally. It seemed to setup auth fine. I did notice that auth for the calm command seemed to be confusingly independent of auth for the list command, but it might've always been like that?

[dbarnett]

All looks good to me and seems to work well. Merging.