support HTTP Basic Auth to download Datomic

To make a long story short, I got the download to work with `wget`, but I couldn't make it work with Chef's `remote_file` resource. I suspect the reason is that `wget` does Basic Auth in way that is more compatible with the Datomic file servers.

This pull request also includes some changes under the hood.

I just noticed that changed the default to a `dev` protocol, which is probably not what you want here, though it is useful on my end.