Node 10.7 integration

[geo2a]

This PR brings the new Ledger and Consensus packages and attempts to integrate them into API.

While preparing this PR, I've encountered several paper cuts that I'd like to get help with:

• I've commented out cardano-rpc from cabal.project, as otherwise cabal cannot construct a build plan for cardano-api. Am I doing something wrong?
• I cannot enter the default nix dev shell, as the shell fails to start with the following error:

error: The option `packages.proto-lens-protobuf-types' does not exist. Definition values:
       - In `<unknown-file>':
           {
             components = {
               library = {
                 build-tools = [
                   <derivation protobuf-30.2>
           ...

Everything is fine on master, so probably the dev shell fails to start because cardano-api does not build, and the error is just Nix being Nix.

As the Nix dev shell does not work for me, I've thrown together an ad-hoc shell.nix. Sharing it below.
shell.nix.txt