Alter the BitcoinCoreInterface._yield_transactions generator to be
nicer in cases where only a small number of transactions need to be
examined. Geometrically ramp the requested number of transactions in
each successive request, starting from 1. Since new transactions can
appear in the Bitcoin Core wallet between RPC calls, overlap successive
request ranges and resume yielding transactions after finding the
previously yielded transaction to avoid yielding duplicates.
The listtransactions RPC of Bitcoin Core can return the same (txid,vout)
as both a "category":"receive" and a "category":"send". Therefore, use
(txid,vout,category) as the sync key to ensure that all distinct
elements are yielded.
Delete the unused wallet_name parameter from _yield_transactions, per
suggestion by Adam Gibson.
Matt Whitlock
8d454277d8