General cleanup: fix some bugs, some refactoring (#65)

* 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

src/routes/mod.rs

@@ -35,9 +35,7 @@ pub fn versions_config(cfg: &mut web::ServiceConfig) {
             web::scope("version")
                 .service(versions::version_get)
                 .service(versions::version_delete)
-                .service(
-                    web::scope("{version_id}").service(version_creation::upload_file_to_version),
-                ),
+                .service(version_creation::upload_file_to_version),
         );
 }