Authentication

[josephg]

Statecraft needs an authentication store.

To make that work we need to pass session information through all operation options objects. It would be ignored by the root stores, but added, passed and handled through stores which are all about that.

We don't need a stable auth store pre 1.0, but I don't want to be adding options after that point.

• Make proof of concept auth store
• Add auth options to fetch / subscribe / getOps / ...
• Pass opaque session information through networking protocol?
• Make simple authentication demo