This is the implementation for the design described in ADR 12[0]. It's
the first step of a larger refactor of the p2p package as tracked in
interface bundling all concerns of low-level connection handling and
isolating the rest of peer lifecycle management from the specifics of
the low-level internet protocols. Even if the swappable implementation
will never be utilised, already the isolation of conn related code in
one place will help with the reasoning about execution path and
addressation of security sensitive issues surfaced through bounty
programs and audits.

We deliberately decided to not have Peer filtering and other management
in the Transport, its sole responsibility is the translation of
connections to Peers, handing those to the caller fully setup. It's the
responsibility of the caller to reject those and or keep track. Peer
filtering will take place in the Switch and can be inspected in a the
following commit.

This changeset additionally is an exercise in clean separation of logic
and other infrastructural concerns like logging and instrumentation. By
leveraging a clean and minimal interface. How this looks can be seen in
a follow-up change.

Design #2069[2]
Refs #2067[3]
Fixes #2047[4]
Fixes #2046[5]

changes:
* describe Transport interface
* implement new default Transport: MultiplexTransport
* test MultiplexTransport with new constraints
* implement ConnSet for concurrent management of net.Conn, synchronous
to PeerSet
* implement and expose duplicate IP filter
* implemnt TransportOption for optional parametirisation

[0] https://github.com/tendermint/tendermint/blob/master/docs/architecture/adr-012-peer-transport.md
[1] https://github.com/tendermint/tendermint/issues/2067
[2] https://github.com/tendermint/tendermint/pull/2069
[3] https://github.com/tendermint/tendermint/issues/2067
[4] https://github.com/tendermint/tendermint/issues/2047
[5] https://github.com/tendermint/tendermint/issues/2046

and fix formatting

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

BlockIntervalSeconds metric & DB tests cleanup & benchmark improv.

otherwise we're benchmarking overriding single key (because hash stays
the same!)

Otherwise, it's impossible to see outliers
https://github.com/tendermint/tendermint/issues/1835#issuecomment-402054099

Why:
original fork is abandoned and not supported anymore.

Changes:
- LevelDB 1.19 (LevelDB and Snappy are both compiled and linked statically, so while you will not need them installed on your target machine, you should have a roughly compatible version of libstdc++.)
- snappy and lz4 libs included by default

Refs #1714

* update DOCS_README
* add spec to docs & other lil fixes (#2402)

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

Refs #2391

* Enforce file permissions in case they've changed

* test behaviour for autofile

* use testify in tests and rename `fInf` to `fileInfo`

* return an error if file permissions have changed

- if we can't read the file, we'll still panic

* get rid of "github.com/pkg/errors" dependency

* address review comments:

- prefix instead of suffix
- add state to err and construct formatting in Error() method

* address review comments:

- move error to libs/errors

Fixes #2409

also, return ErrNotStarted when trying to stop a not-running service

* 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

* remove ConsensusParams.TxSize and ConsensusParams.BlockGossip

Refs #2347

* block part size is now fixed

Refs #2347

* use max data size, not max bytes for tx limit

Refs #2347

* md links dont work in slate

* docs: link to rpc

* docs: use unsafe_reset_all

* do not advertise unsafe_reset_priv_validator

* Start of ADR

* flesh out abci events and errors adrs

* adr: move 012 to 023

* adr-022: add note from cwgoes

Merge master back to develop

Release/v0.24.0

Fix typos in spec

update UPGRADING.md and minor docs fixes

Major spec update to prepare v0.24.0 for release

* 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

add script to add links in changelog