* Merged mod file upload in version creation, mod creation and
version file add to one function; This makes sure that they are
consistent
* Made some fields on `User` optional: `github_id`, `avatar_url`, `bio`.
* We may not want to publicly show the `github_id` to everyone
with access to the API
* If we allow non-github users, some of those fields would be
invalid; some oauth providers may not have avatars or bios
* Made CORS origins should configurable
* Made `--reconfigure-indices` and `--reset-indices` exit after
completion instead of starting the server
