remove custom configs from the spark mirror

This is a PR to remove all the Shopify custom spark configuration files from the spark repo.  The reason is cluster config is taken care of by chef. The only repo that uses these configs are starscream and should be identical to chef in most cases, except local development. So I would vote for taking any required starscream related configs and putting them there __or__ having a central shopify spark config repo which is kept up to date for all spark related projects. The reason to do this would be:

1. keep spark mirror clean
2. avoid forgetting to set configs in multiple locations

thoughts @airhorns @udnay ?