* les: reject client connection if it makes too much invalid req

* les: address comments

* les: use uint32

* les: fix variable name

* les: add invalid counter for duplicate invalid req

renamed NewKeyStoreFromTransactor to NewKeystoreTransactor
fixed godoc

les/handler: avoid lookup missing state

eth: enforce stricter known limits on idle peers

EIP-695 was written in 2017. Parity and Infura have support for this
method and we should, too.

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.

* eth, les: reject stale request

* les: reuse local head number

core, ethdb, metrics, p2p: expose various counter metrics for grafana

* Fix file system access for Windows

* Encapsulate file accesses

* Style fixes

* vendor: remove unused dependencies

These were used by swarm code, which has now migrated to its own repository.

* travis.yml: remove sudo requirement for test builders

These needed sudo to run FUSE tests for swarm.

* 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

vendor: pull in USB fix for docker (alpine/musl)

Github has started supporting SECURITY.md to contain a project's security policy. Adding this information to the repository makes it easier to determine how to disclosure a vulnerability as SECURITY.md becomes a standard.

The pgp fingerprint and key is taken from bounty.ethereum.org.

vendor: pull fixed usb library for nocgo builds

This makes the test work if NetworkId is changed in forks of go-ethereum.

account/usbwallet: abort usb enumeration after failures

* cmd/clef: Enable smartcard hub

* clef: don't error is pcsc is not installed

* Add retesteth command

* Remove label and insert full version

* mineBlock - break the inner loop when the block is full

* Fixes for touched non-reward accounts, gas limit issues

* Not fail when SendTx has transaction with incorrect RLP

* Fix linter (unnecessary conversion)

* retesteth: add usage string to flag

* scwallet: don't error when pcsc socket is missing

* review feedback

* more review feedback

accounts/usbwallet: add webusb trezor support

TransactionInBlock crashed if json was nil and there was an error
because it tried to access fields `From` and `BlockHash` of the nil object.

* core/signer, clef: improve ui-test flow, fix errors in uint handling for eip-712

* core/signer: add fuzzer testcases + crashfixes

* signer: address review concerns, check sign in integer parsing