Implement `sync-label` bin script + clean up

Add a sync scripts to synchronize all shared labels across all team
projects. The configuration is stored in a file, so that it's easy
to re-run it later.

Add a config file for the loopback/studio team.

`create-client`: read credentials from a file

`package`: add repository field

/to @ritch please review
/cc @sam-github @altsang @chandadharap