We are swapping the exisiting listener implementation with the newly
introduced Transport and its default implementation MultiplexTransport,
removing a large chunk of old connection setup and handling scattered
over the Peer and Switch code. The Switch requires a Transport now and
handles externally passed Peer filters.

* ignore existing peers in DialPeersAsync

Fixes #2253

* rename HasPeerWithAddress to IsDialingOrExistingAddress

[breaking] remove Switch#IsDialing

* check if addrBook is nil

to be consistent with other usages of addrBook across Switch

* different log messages for 2 use-cases

* [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

* libs: Remove usage of custom Fmt, in favor of fmt.Sprintf

Closes #2193

* Fix bug that was masked by custom Fmt!

* p2p/pex: Allow configured seed nodes to be offline

Previously you couldn't startup tendermint if a seed node was offline.
This now allows you to startup tendermint, as long as all seed node addresses
are formatted correctly. In the event that all seed nodes are down,
and the address book is empty, then it crashes with an informative error msg.
(This case doesn't occur if no seeds were specified)

Closes #1716

* (Squash this) Address melekes' comments

* (squash this) fix package imports

* (squash this) fix pex_reactor comment

* (squash this) add a test case

also, remove excessive log message

Refs #2072

This is to reduce wait times when initially connecting. This still runs checks
such as whether you still want additional peers.

A test case has been created, which fails if this change is not included.

* Removed unnecessary onStart & onStop calls in reactor

* Refactor OnStart & OnStop in reactor

* Removed redundant OnStart func in reactor

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

Refs #1720

* Add private peer ID tracking to AddrBook

* Remove private peer tracking/blocking from pex

* debug level msg when we fail to add private address

This commit switches all usage of math/rand to cmn's rand. The only
exceptions are within the random file itself, the tools package, and the
crypto package. In tools you don't want it to lock between the go-routines.
The crypto package doesn't use it so the crypto package have no other
dependencies within tendermint/tendermint for easier portability.

Crypto/rand usage is unadjusted.

Closes #1343

This reverts commit d02c5d1e30.

Refs #646

Refs #646

* new config option for external address to advertise
* if blank, defaults to best guess from listener
* if laddr ip address is also blank, default to IPv4

Fixes #1830

remember that PeerSet#Get can return nil

* config: rename skip_upnp to upnp

Change default option to enable upnp.

Closes #1806

* doc updates

- fix comment and set UPNP to false in TestP2PConfig
- add UPNP to config template
- update changelog

This reverts commit 96a3502

As both configs are concerned with the p2p packaage and PeerConfig is
only used inside of the package there is no good reason to keep the
couple of fields separate, therefore it is collapsed into the more
general P2PConifg. This is a stepping stone towards a setup where the
components inside of p2p do not have any knowledge about the config.

follow-up to #1325

In some scenarios like tests we want to disable the guard which prevents
peers connecting from the same ip.

Fixes #1632
Closes #1634

* fix before/after in isBad()
* allow multiple IPs per ID even if ID isOld