Support protocol 7 API changes

[Victor-N-Suadicani]

Purpose

Addresses #192.

Changes

I updated the concordium-base submodule to point to this commit from this PR which I understand is related to the API changes. This updated the gRPC API submodule in concordium-base, which allowed me to regenerate the protobuf code. I then naively fixed the errors that resulted from the changed generated code.

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.

[td202]

What's currently missing is addressing the changes to PoolInfoResponse. In particular, I'd suggest restructuring BakerPoolStatus to match this. That is, baker_equity_capital, delegated_capital, delegated_capital_cap, pool_info and baker_stake_pending_change are moved into a separate ActiveBakerPoolStatus, which is optional (and should be present if and only if the pool_info is present on the PoolInfoResponse).

[td202]

Looks good. Be sure to update the changelog.

[Victor-N-Suadicani]

@td202 I think you should probably merge your PR on base first (Concordium/concordium-base#534) as this depends on that through the submodule.

[limemloh]

Please update the Node version compatibility version in the readme as well

[Victor-N-Suadicani]

@limemloh how do I know which version is the new compatible one?