EthStore was only being used for tracking account balances and nonces now, so I removed its block-tracking duties, renamed it account-tracker, and removed it as a dependency from `KeyringController`, so that KRC can go live on without a hard dep on it.
- Was incorrectly calling some eth-query methods (left over from old local eth-query)
- Was still passing block to getAccount in addAccount
- Now emitting update only after all account balances are loaded, reducing UI update traffic.