* github: config for probot-stale bot

* github: use stale label, instead of wontfix

* core/vm, crypto/bn256: switch over to cloudflare library

* crypto/bn256: unmarshal constraint + start pure go impl

* crypto/bn256: combo cloudflare and google lib

* travis: drop 386 test job

cmd/evm, core/vm, internal/ethapi: don't disable call gas metering

* utils: fix #16138 by checking if vhosts flag is set

* utils,node: fix defaults for rpcvhosts

* node,utils: address review concerns

whisper: refactoring go-routines workflow

Move the call mailServer.Init() down (to the bottom of the function) because if the function initialize() completes successfully, then it will be followed by mailServer.Close() in shutdown(). The workflow of the corresponding goroutines is clearer now.

accounts/abi: Abi binding support for nested arrays, fixes #15648, including nested array unpack fix (#15676)

* accounts/abi/bind: support for multi-dim arrays

Also:
- reduce usage of regexes a bit.
- fix minor Java syntax problems

Fixes #15648

* accounts/abi/bind: Add some more documentation

* accounts/abi/bind: Improve code readability

* accounts/abi: bugfix for unpacking nested arrays

The code previously assumed the arrays/slices were always 1 level
deep. While the packing supports nested arrays (!!!).

The current code for unpacking doesn't return the "consumed" length, so
this fix had to work around that by calculating it (i.e. packing and
 getting resulting length) after the unpacking of the array element.
It's far from ideal, but unpacking behaviour is fixed now.

* accounts/abi: Fix unpacking of nested arrays

Removed the temporary workaround of packing to calculate size, which was
incorrect for slice-like types anyway.
Full size of nested arrays is used now.

* accounts/abi: deeply nested array unpack test

Test unpacking of an array nested more than one level.

* accounts/abi: Add deeply nested array pack test

Same as the deep nested array unpack test, but the other way around.

* accounts/abi/bind: deeply nested arrays bind test

Test the usage of bindings that were generated
for methods with multi-dimensional (and not
just a single extra dimension, like foo[2][3])
array arguments and returns.

edit: trigger rebuild, CI failed to fetch linter module.

* accounts/abi/bind: improve array binding

wrapArray uses a regex now, and arrayBindingJava is improved.

* accounts/abi: Improve naming of element size func

The full step size for unpacking an array
 is now retrieved with "getFullElemSize".

* accounts/abi: support nested nested array args

Previously, the code only considered the outer-size of the array,
ignoring the size of the contents. This was fine for most types,
but nested arrays are packed directly into it, and count towards
the total size. This resulted in arguments following a nested
array to replicate some of the binary contents of the array.

The fix: for arrays, calculate their complete contents size:
 count the arg.Type.Elem.Size when Elem is an Array, and
 repeat when their child is an array too, etc.
The count is the number of 32 byte elements, similar to how it
 previously counted, but nested.

* accounts/abi: Test deep nested arr multi-arguments

Arguments with a deeply nested array should not cause the next arguments
to be read from the wrong position.

whisper: close the `done` channel in one location

whisper: filereader mode introduced to wnode

cmd/faucet: update state in background, skip when busy

Replace "atleast" with "at least" in the manifest error message.

whisper: topics replaced by bloom filters in mailserver communication

* metrics: add sleep to test in order to get predictable output

* metrics: relax constraints on timer test

The diagnostic tool was saving the unencrypted version of the messages, which is an obvious
security flaw. As of this commit:
  * encrypted messages saved instead of plain text.
  * all messages are stored, even that created by the user of wnode.

whisper: message filtering optimization

Only run the message through filters who registered their interest.

whisper: fixed dataraces in peer unit tests

whisper: mailserver no longer supports the signature validation

Mailserver is provided as an example, but client validation belongs to the upper layer protocol and
needs not be covered in this example. The check that was previously available hinders the switch
to libp2p so we agreed not to include that check in that example code anymore.

internal/ethapi: fix getTransactionReceipt

travis, build, consensus: drop support for Go 1.7

The function would return false for numbers, so isLetter is a more
accurate description of the behavior.