Pseudocode for core-consensus protocol

[liamsi]

Summary

We use tendermint but already incorporated some changes in the core protocol and plan to do more changes. IMO, it is required to have a high-level description of the consensus including a very simple abstraction of the ABCI boundary.

This work is a really example in my opinion:

• original tendermint pseudocode in markdown: https://github.com/tendermint/spec/blob/5de8bbf46817b279bf6053893ab4f98ac26853b7/spec/abci%2B%2B/v0.md
• changes proposed by @ValarDragon for abci++: https://github.com/tendermint/spec/blob/5de8bbf46817b279bf6053893ab4f98ac26853b7/spec/abci%2B%2B/v4.md#tendermint-v3-markdown-pseudocode

Action Items

Open separate issues about these:

• describe the current LL implementation consensus (basically including preprocess phase)
• specify future required changes
  • changes to preprocess phase to include intermediate state roots
  • FinalizeBlock?
  • AFAIR, even the simple version of fee-burning required some changes to ABCI
  • later (after devnet): immediate execution