Implements #72, attribute uniqueness. This extends schema to have a field "unique" which means a value should be unique for that object, and all other live objects (recycle and tombstones excluded). Note UUID has to retain special handling in base.rs and can't usethis due to needing to check with recycled too..
This adds support for authentication and credential storage to the server.
It also adds account recovery and options for integration test fixtures, refactors
to make the client library easier to manage, and support clean seperation of the
proto vs lib.
