* 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)

* abci: codespace

* changelog

* types: Remove pubkey from validator hash

* undo lock file change

* Update Spec

* docs: fix links

* docs: add readme from each section to the sidebar

* docs: links to dirs need a slash

* docs/spec/abci: consensus params and general merkle

* remove some XXX

* config: remove Mempool.RecheckEmpty

* docs: remove recheck_empty

* minor doc cleanup

* docs/tools: link fixes and readme

* docs/networks: networks/local/README.md

* docs: update vuepress config

* docs: 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

* docs: link consensus to blockchain spec. closes #2422

* docs: deprecate research section. closes #2401

* docs: fix some links

* docs: fix some markdown lists

* docs: fix more links

* mempool: update some comments

* make build_c

* docs: notes about databases and WAL files

* docs: determinism. closes #1279

* docs: small note about query paths. closes #2090

* docs: gas

* docs: abci consensus params

* ungitignore
* add docs/.vuepress to enable local builds
* config.js needs to be here, one less step
* docs: make spec in sidebar nicer
* docs: local build instructions

* follow up to removing some consensus params Refs #2382
* change args type to int64 in state#makeParams
* make valsCount and evidenceCount ints again
* MaxEvidenceBytesPerBlock: include magic number in godoc
* [spec] creating a proposal
* test state#TxFilter
* panic if MaxDataBytes is less than 0
* fixes after review
* use amino#UvarintSize to calculate overhead
0c74291f3b/encoder.go (L85-L90)
* avoid cyclic imports
* you can do better Go, come on
* remove testdouble package

and fix formatting

Refs https://github.com/tendermint/tendermint/pull/2417#discussion_r218080500

* [rpc] transform /status result.node_info.other into map
* amino does not support maps, duh

Refs #2391

* Make mempool aware of MaxGas requirement

* update spec

* Add tests

* Switch GasWanted from kv store to persistent kv store

* Fix typo in test name

* switch back to using kvstore, not persistent kv store

* move spec/software/abci.md to spec/abci/apps.md and improve it
* move some of app-dev/app-development.md to spec/abci/client-server.md

* better overview section
* section on tags
* remove notes about state/concurrency from CheckTx
* incorporate feedback from #2249
* explain how validator set updates effect future blocks

* addr_book_strick=false on local nets

* link to spec

* spec: remove TODO, see #1749 instead

* spec: make issues from TODOs

* update docs on addr_book_strict option

* Implement BFT time

* set LastValidators when creating state in state helper

for heights >= 2

* mempool: Store txs by hash inside of cache

This allows for large cachesizes, without fear of the memory
consumption growing rapidly.

* (squash this) rename hashedTx -> txHash

* lint docs with write-good, stop-words

* remove package-lock.json

* update changelog

* fix wrong paragraph formatting

* fix some docs formatting

* fix docs format

* fix abci spec format

* [p2p/pex] connect to more than 10 peers

also, remove DefaultMinNumOutboundPeers because a) I am not sure it's
needed b) it's super confusing

look closely

```
maxPeers := sw.config.MaxNumPeers - DefaultMinNumOutboundPeers
if maxPeers <= sw.peers.Size() {
  sw.Logger.Info("Ignoring inbound connection: already have enough peers", "address", inConn.RemoteAddr().String(), "numPeers", sw.peers.Size(), "max", maxPeers)
```

we print maxPeers = config.MaxPeers - DefaultMinNumOutboundPeers. So we
may not have enough peers even though we say we have enough.

Refs #2130

* update spec

* replace MaxNumPeers with MaxNumInboundPeers/MaxNumOutboundPeers

Refs #2130

* update changelog

* make max rpc conns formula visible to users

* update spec

* docs: note max outbound peers excludes persistent

Refs #1134

Validation:

- ignored in block.ValidateBasic since it's stateful information
- checked in blockExec.ValidateBlock

This now uses one hkdf on the X25519 shared secret to create
a key for the sender and receiver.
The hkdf call is now just called upon the computed shared
secret, since the shared secret is a function of the pubkeys.

The nonces now start at 0, as we are using chacha as a stream
cipher, and the sender and receiver now have different keys.

Refs #1706

Currently the top level directory contains basically all of the code
for the crypto package. This PR moves the crypto code into submodules
in a similar manner to what `golang/x/crypto` does. This improves code
organization.

Ref discussion: https://github.com/tendermint/tendermint/pull/1966

Closes #1956

* docs: deprecate specification dir, closes #1814

* update genesis

* old spec dir, deprecation complete

* rm a file

This reverts commit d02c5d1e30.