The new config loader requires some steps to happen in a different
order, particularly in regard to knowing the schema in order to
decode the configuration.
Here we lean directly on the configschema package, rather than
on helper/schema.Backend as before, because it's generally
sufficient for our needs here and this prepares us for the
helper/schema package later moving out into its own repository
to seed a "plugin SDK".
Move the Swift State from a legacy remote state to an official backend.
Add `container` and `archive_container` configuration variables, and deprecate `path` and `archive_path` variables.
Future improvements: Add support for locking and environments.
Martin Atkins