Code and test performance of a prototype replacement of get_account_history API implemented in hivemind/postgres

This task requires a hivemind database that has been supplemented with the data provided by the new hived plugin that stores block meta data and operations history to a postgres database.

Implementation should be relatively simple, but there's a couple performance metrics to measure: API latency, performance under load conditions, and ability to filter further into the past than was reasonably achievable using the hived API (hopefully, we can remove all limitations on how far back a request of a filtered set of operations can go).