Save multiple elements in a Stream

I noticed that when calling `saveAll` on a `Stream`, it doesn't actually materialize all the elements in the stream. This seems like the wrong behavior. You would expect all the elements to be saved within the transaction. Instead, the saves only happen when you access the elements of the resulting collection.

I fixed the issue by converting to an `IndexedSeq` in `saveAll` which forces all the elements to be computed.