This adds all dashboard changes from the last couple months.
We're about to remove the dashboard, but decided that we should
get all the recent work in first in case anyone wants to pick up this
project later on.

* cmd, dashboard, eth, p2p: send peer info to the dashboard
* dashboard: update npm packages, improve UI, rebase
* dashboard, p2p: remove println, change doc
* cmd, dashboard, eth, p2p: cleanup after review
* dashboard: send current block to the dashboard client

* p2p/enode: add Iterator and associated utilities

* p2p/discover: add RandomNodes iterator

* p2p: dial using iterator

* cmd/devp2p: add discv4 crawler

* cmd/devp2p: WIP nodeset filter

* cmd/devp2p: fixup lesFilter

* core/forkid: add NewStaticFilter

* cmd/devp2p: make -eth-network filter actually work

* cmd/devp2p: improve crawl timestamp handling

* cmd/devp2p: fix typo

* p2p/enode: fix comment typos

* p2p/discover: fix comment typos

* p2p/discover: rename lookup.next to 'advance'

* p2p: lower discovery mixer timeout

* p2p/enode: implement dynamic FairMix timeouts

* cmd/devp2p: add ropsten support in -eth-network filter

* cmd/devp2p: tweak crawler log message

This updates the DNS TXT record format to the latest
changes in ethereum/EIPs#2313.

This adds an implementation of node discovery via DNS TXT records to the
go-ethereum library. The implementation doesn't match EIP-1459 exactly,
the main difference being that this implementation uses separate merkle
trees for tree links and ENRs. The EIP will be updated to match p2p/dnsdisc.

To maintain DNS trees, cmd/devp2p provides a frontend for the p2p/dnsdisc
library. The new 'dns' subcommands can be used to create, sign and deploy DNS
discovery trees.

Most of these changes are related to the Go 1.13 changes to test binary
flag handling. 

* cmd/geth: make attach tests more reliable

This makes the test wait for the endpoint to come up by polling
it instead of waiting for two seconds.

* tests: fix test binary flags for Go 1.13

Calling flag.Parse during package initialization is prohibited
as of Go 1.13 and causes test failures. Call it in TestMain instead.

* crypto/ecies: remove useless -dump flag in tests

* p2p/simulations: fix test binary flags for Go 1.13

Calling flag.Parse during package initialization is prohibited
as of Go 1.13 and causes test failures. Call it in TestMain instead.

* build: remove workaround for ./... vendor matching

This workaround was necessary for Go 1.8. The Go 1.9 release changed
the expansion rules to exclude vendored packages.

* Makefile: use relative path for GOBIN

This makes the "Run ./build/bin/..." line look nicer.

* les: fix test binary flags for Go 1.13

Calling flag.Parse during package initialization is prohibited
as of Go 1.13 and causes test failures. Call it in TestMain instead.

Original change by @jpeletier 

Fixed assigning values to variables we don't end up using.

No need to convert these types.

Make it select from all live nodes instead of selecting the heads of
random buckets.

* eth: chain config (genesis + fork) ENR entry

* core/forkid, eth: protocol independent fork ID, update to CRC32 spec

* core/forkid, eth: make forkid a struct, next uint64, enr struct, RLP

* core/forkid: change forkhash rlp encoding from int to [4]byte

* eth: fixup eth entry a bit and update it every block

* eth: fix lint

* eth: fix crash in ethclient tests

This entry was an experiment, but we're moving on to the
entry-per-protocol instead.

* all: implement simple checkpoint syncing

cmd, les, node: remove callback mechanism

cmd, node: remove callback definition

les: simplify the registrar

les: expose checkpoint rpc services in the light client

les, light: don't store untrusted receipt

cmd, contracts, les: discard stale checkpoint

cmd, contracts/registrar: loose restriction of registeration

cmd, contracts: add replay-protection

all: off-chain multi-signature contract

params: deploy checkpoint contract for rinkeby

cmd/registrar: add raw signing mode for registrar

cmd/registrar, contracts/registrar, les: fixed messages

* cmd/registrar, contracts/registrar: fix lints

* accounts/abi/bind, les: address comments

* cmd, contracts, les, light, params: minor checkpoint sync cleanups

* cmd, eth, les, light: move checkpoint config to config file

* cmd, eth, les, params: address comments

* eth, les, params: address comments

* cmd: polish up the checkpoint admin CLI

* cmd, contracts, params: deploy new version contract

* cmd/checkpoint-admin: add another flag for clef mode signing

* cmd, contracts, les: rename and regen checkpoint oracle with abigen

The dialer limits itself to one attempt every 30s. Apply the same limit
in Server and reject peers which try to connect too eagerly. The check
against the limit happens right after accepting the connection.

Further changes in this commit ensure we pass the Server logger
down to Peer instances, discovery and dialState. Unit test logging now
works in all Server tests.

* p2p/enr: add entries for for IPv4/IPv6 separation

This adds entry types for "ip6", "udp6", "tcp6" keys. The IP type stays
around because removing it would break a lot of code and force everyone
to care about the distinction.

* p2p/enode: track IPv4 and IPv6 address separately

LocalNode predicts the local node's UDP endpoint and updates the record.
This change makes it predict IPv4 and IPv6 endpoints separately since
they can now be in the record at the same time.

* p2p/enode: implement base64 text format
* all: switch to enode.Parse(...)

This allows passing base64-encoded node records to all the places that
previously accepted enode:// URLs. The URL format is still supported.

* cmd/bootnode, p2p: log node URL instead of ENR

...and return the base64 record in NodeInfo.

* p2p/discover: export Ping and RequestENR

These two are useful for checking the status of a node.

* cmd/devp2p: add devp2p debug tool

This is a new tool for debugging p2p issues. It supports a few
basic tasks for now, but many more things can and will be added
in the near future.

   devp2p enrdump            -- prints ENRs readably
   devp2p discv4 ping        -- checks if a node is up
   devp2p discv4 requestenr  -- gets a node's record
   devp2p discv4 resolve     -- finds a node through the DHT

* p2p: remove direct import of cgo-library

* accounts, rpc: more nocgo alternatives

* rpc: move unix path constant into separate file

* accounts/scwallet: address review concerns, remove copy-pasta

This change implements EIP-868. The UDPv4 transport announces support
for the extension in ping/pong and handles enrRequest messages.

There are two uses of the extension: If a remote node announces support
for EIP-868 in their pong, node revalidation pulls the node's record.
The Resolve method requests the record unconditionally.

swarm/storage/localstore: fix broken metric (#1373)

p2p/protocols: count different messages (#1374)

cmd/swarm: disable snapshot create test due to constant flakes (#1376)

swarm/network: remove redundant goroutine (#1377)

cmd/swarm/swarm-smoke: improve smoke tests (#1337)

swarm/network: remove dead code (#1339)

swarm/network: remove FetchStore and SyncChunkStore in favor of NetStore (#1342)

This change restructures the internals of p2p/discover to make room for
the discv5 code which will soon be added to this package.

- packet type names now have a "V4" suffix.
- ListenUDP returns *UDPv4 instead of *Table. This technically breaks
  the API but the only caller in go-ethereum is package p2p, which uses
  a compatible interface and doesn't need changes.
- The internal transport interface is changed to make Table reusable for v5.
- The 'lookup' code moves from table to transport. This required
  updating the lookup unit test to use udpTest instead of a custom transport.

* swarm/network: fix data races in TestInitialPeersMsg test

* swarm/network: add Kademlia.Saturation method with lock

* swarm/network: add Hive.Peer method to safely retrieve a bzz peer

* swarm/network: remove duplicate comment

* p2p/testing: prevent goroutine leak in ProtocolTester

* swarm/network: fix data race in newBzzBaseTesterWithAddrs

* swarm/network: fix goroutone leaks in testInitialPeersMsg

* swarm/network: raise number of peer check attempts in testInitialPeersMsg

* swarm/network: use Hive.Peer in Hive.PeerInfo function

* swarm/network: reduce the scope of mutex lock in newBzzBaseTesterWithAddrs

* swarm/storage: disable TestCleanIndex with race detector