concord-server-db: option to host process log tables in separate DB

[ibodrov]

An option to help optimize/offload some the DB load.

No schema changes necessary if the same DB is used (as before).

Fully separate DBs is just an idea for now, the actual implementation would require a way to migrate from a single DB instance to an instance with the separate log DB. Still, useful for performance tuning.

TODO: ProcessCleaner