* Consistent order fields of Timestamp/BlockID fields in CanonicalVote and
CanonicalProposal
* update spec too
* Introduce and use IsZero & IsComplete:
- update IsZero method according to spec and introduce IsComplete
- use methods in validate basic to validate: proposals come with a
"complete" blockId and votes are either complete or empty
- update spec: BlockID.IsNil() -> BlockID.IsZero() and fix typo
* BlockID comes first
* fix tests
* WIP: switching to fixed offsets for SignBytes
* add version field to sign bytes and update order
* more comments on test-cases and add a tc with a chainID
* remove amino:"write_empty" tag
- it doesn't affect if default fixed size fields ((u)int64) are
written or not
- add comment about int->int64 casting
* update CHANGELOG_PENDING
* update documentation
* add back link to issue #1622 in documentation
* remove JSON tags and add (failing test-case)
* fix failing test
* update test-vectors due to added `Type` field
* change Type field from string to byte and add new type alias
- SignedMsgType replaces VoteTypePrevote, VoteTypePrecommit and adds new
ProposalType to separate votes from proposal when signed
- update test-vectors
* fix remains from rebasing
* use SignMessageType instead of byte everywhere
* fixes from review
* switch to amino for SignBytes and add Reply with error message
- currently only Vote is done
* switch Reply type in socket for other messages
- add error description on error
* add TODOs regarding error handling
* address comments from peer review session (thx @xla)
- contains all changes besides the test-coverage / error'ing branches
* increase test coverage:
- add tests for each newly introduced error'ing code path
* return error if received wrong response
* add test for wrong response branches (ErrUnexpectedResponse)
* update CHANGELOG_PENDING and related documentation (spec)
* fix typo: s/CanonicallockID/CanonicalBlockID
* fixes from review
