Configuration: schema and migration system

`config` - system for deprecating old configs

`config.schema` - schema
- dataclasses
- typed dicts
- shapes
- whatever it takes to take a `dict`-like structure

`config.v` - old versions
`config/v/` - an old version is tagged whenever new one is
`config/v/tests/test_config.py` tests / assertions for schema to migrate to new one, load old ones with deprecation warning