Add support of local and distributed store

[MainRo]

Stateful operations use memory based stores for now. We need support of a local store to limit memory consumption in context intensive applications, and support of distributed store to resume correctly an application and manage rebalancing.

Local store should be rocksdb, like on kafka streams and faust.
Distributed store is a kafka compacted topic.

This depends on maki-nage/rxsci#2