We're now directly using Greg's unmodified banlist which
simplifies the update process.
The banlist package with its dependency on the bitcoin datadir path is only
relevant for internal use within nix-bitcoin, so we can safely remove
it.
We're now using the bitcoin-cli from `services.bitcoind.package`.
Fixes#129
Without this, starting the virtualbox guest service fails during machine activation.
This is due to an incompatible NixOS machine base image.
Fix this by using an updated version of nixops.
Erik Arvstedt