Protobuf upgrade

[fazo96]

Status is that it works, tests are passing, but it needs cleanup

Notes for discussion

• deprecated optional fields are problematic, I removed them. We should also rename some other fields that were named not to conflict with existing deprecated fields (like sig)
• missing marketplace and vendor signatures of the marketplace-vendor key in PoPR. I added these fields back in, or we could create a separate IPFS datastructure for the vendor-marketplace key that contains these signatures so they are not repeated in all review records
• verifiable useless? just check if verification is present and make it optional
• // vendor key location and vendor encryption key location should resolve from the did vendor_did field is enough
• when signing, we calculate the internal hash of PoPR/RR and then create the signature and set it. When we calculate the internal hash we remove the signature. The sig fields are however required, so we have to set a bogus/empty constant signature. The quick solve is to make signatures not required in the protobuf
• some shortcuts in the code, need to review TODOs I left
• in signature.type what should we put? Signature algorithm should go here
• other protobuf libraries not tested yet stick with protons for now
• need to diff compare the implementation protobuf I modified with the protocol ones to see exactly what was changed
• dates are unix timestamps

Issues

• dates/timestamps are all zero: https://github.com/ChluNetwork/chlu-ipfs-support/issues/94
• importUnverifiedReviews is inefficient https://github.com/ChluNetwork/chlu-ipfs-support/issues/95
• DID of the customer gets autopublished when publishing a review https://github.com/ChluNetwork/chlu-ipfs-support/issues/97

Switching protocol buffer library

• we are using: https://github.com/ipfs/protons
• which is a fork of https://github.com/mafintosh/protocol-buffers
• there is also https://github.com/dcodeIO/protobuf.js
• and finally google's official https://github.com/google/protobuf/tree/master/js

[kulpreet]

Quick one about the signature type. We need to switch to a well know signature suite. I created a card here https://trello.com/c/MhYIkZlY, we can discuss what this means for the current choices and what we need to change.