* refactor packages, flags, subscriptions
* DRY refactor builder tests
* use mockgen to generate mocks
* update README
* MODE=statediff no longer needed for unit tests
* simplify func names, clean up metrics
* move write params to service field
* sql indexer: confirm quit after ipld cache reset
prevents negative waitgroup panic
* don't let TotalDifficulty become nil
* use forked plugeth, plugeth-utils for now
