Implements https://github.com/cerc-io/go-ethereum/issues/319
With this we can perform a single pass to process updates.
Also
* refactor code structure around single-pass iteration
* refactor builder metrics to match new set of functions
* fix unit tests by running sequentially
* update ipld-eth-db in compose
* factor out fixture data into external module
* some CI updates
Reviewed-on: #11
* 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
