* types: add Version to Header
* abci: add Version to Header
* state: add Version to State
* node: check software and state protocol versions match
* update changelog
* docs/spec: update for versions
* state: more tests
* remove TODOs
* remove empty test
* require block.Time of the fist block to be genesis time
Refs #2587:
```
We only start validating block.Time when Height > 1, because there is no
commit to compute the median timestamp from for the first block. This
means a faulty proposer could make the first block with whatever time
they want.
Instead, we should require the timestamp of block 1 to match the genesis
time.
I discovered this while refactoring the ValidateBlock tests to be
table-driven while working on tests for #2560.
```
* do not accept blocks with negative height
* update changelog and spec
* nanos precision for test genesis time
* Fix failing test (#2607)
- state.MakeBlock takes a proposerAddr
- validateBlock only checks that the ProposerAddress is in the validator
set
- fix raceyness from bad proposer test:
- use privValidator to get the proposer address (instead of racy
state)
- note we had to remove the test that checked the correct proposer was
included for higher rounds because we don't have a good way to test
this with multiple consensus states and not using the
privValidator.Address while calling createProposalBlock was a hack!
