storage: first API design and 2 implementations: DictStore and JsonStore
storage: change the API to constraint the value to be a dict. Implement find() method, and update examples / unit tests.
storage: add count() and keys()
storage: add container emulation for synchronous API.
storage: add clear()
storage: new RedisStore()
storage: update versionadded
Merge branch 'feature-storage-api'