Note: implement flow

[VictorTrustyDev]

Nothing here, just my notes for tracking

• feat(test+rpc): add integration test util + add IT skeleton for Json-RPC #74
• fix(rpc): compute and return correct transactionsRoot and receiptsRoot hashes #85 (contains TODO)
• imp(indexer): make EVMTxIndexer mandatory service, starts before Json-RPC #96
• imp(test): add some edge test cases + benchmark tests #100