This commit adds pluggable consensus engines to go-ethereum. In short, it
introduces a generic consensus interface, and refactors the entire codebase to
use this interface.

* main,import: Add --nocompaction flag + multiple import files

* geth/import: documentation

* import: Added more info to err message

* fix :P

* accounts, cmd, eth, ethdb: port logs over to new system

* ethdb: drop concept of cache distribution between dbs

* eth: fix some log nitpicks to make them nicer

This command was meant as a hackish way to upgrade our chain database way back
when nobody cared for live updates and the size of the database along with its
import times was small. With the current database weighing hundreds of GBs and
processing times of many days, this command is just ludicrous.

* cmd/geth: added 'geth bug' command

Added bug command to geth, which will open a browser window
with an issue template and some additional system information.

* cmd/geth: update bug with better infos

* cmd/geth: added browser fallback

* cmd/geth: govet yo momma

Reworked the EVM gas instructions to use 64bit integers rather than
arbitrary size big ints. All gas operations, be it additions,
multiplications or divisions, are checked and guarded against 64 bit
integer overflows.

In additon, most of the protocol paramaters in the params package have
been converted to uint64 and are now constants rather than variables.

* common/math: added overflow check ops
* core: vmenv, env renamed to evm
* eth, internal/ethapi, les: unmetered eth_call and cancel methods
* core/vm: implemented big.Int pool for evm instructions
* core/vm: unexported intPool methods & verification methods
* core/vm: added memoryGasCost overflow check and test

This reverts commit 8b57c494.

- Handle a data race where a Ledger drops between list and open
- Prolong Ledger tx confirmation window to 30 days from 1 minute
- Simplify Ledger chainid-signature calculation and validation
- Simplify Ledger USB APDU request chunking algorithm
- Silence keystore account cache notifications for manual actions
- Only enable self derivations if wallet open succeeds

Reworked the EVM gas instructions to use 64bit integers rather than
arbitrary size big ints. All gas operations, be it additions,
multiplications or divisions, are checked and guarded against 64 bit
integer overflows.

In additon, most of the protocol paramaters in the params package have
been converted to uint64 and are now constants rather than variables.

* common/math: added overflow check ops
* core: vmenv, env renamed to evm
* eth, internal/ethapi, les: unmetered eth_call and cancel methods
* core/vm: implemented big.Int pool for evm instructions
* core/vm: unexported intPool methods & verification methods
* core/vm: added memoryGasCost overflow check and test

cmd/geth: tidied up the source

All account's nonce start at 0.

This commit converts the dependency management from Godeps to the vendor
folder, also switching the tool from godep to trash. Since the upstream tool
lacks a few features proposed via a few PRs, until those PRs are merged in
(if), use github.com/karalabe/trash.

You can update dependencies via trash --update.

All dependencies have been updated to their latest version.

Parts of the build system are reworked to drop old notions of Godeps and
invocation of the go vet command so that it doesn't run against the vendor
folder, as that will just blow up during vetting.

The conversion drops OpenCL (and hence GPU mining support) from ethash and our
codebase. The short reasoning is that there's noone to maintain and having
opencl libs in our deps messes up builds as go install ./... tries to build
them, failing with unsatisfied link errors for the C OpenCL deps.

golang.org/x/net/context is not vendored in. We expect it to be fetched by the
user (i.e. using go get). To keep ci.go builds reproducible the package is
"vendored" in build/_vendor.

This change ensures that nodes started with different Name but same
DataDir values don't use the same nodekey and IPC socket.

This change also deletes generator.go, moving the only interesting line
in it into release.go. The binding has been regenerated with abigen from
develop and solc v0.3.6.

As per GNU GPL requirement I've added the copyright and the license
information as a subcommand as well as a copyright notice when
displaying the help command.

The account manager was previously created by packge cmd/utils as part
of flag processing and then passed down into eth.Ethereum through its
config struct. Since we are starting to create nodes which do not have
eth.Ethereum as a registered service, the code was rearranged to
register the account manager as its own service. Making it a service is
ugly though and it doesn't really fix the root cause: creating nodes
without eth.Ethereum requires duplicating lots of code.

This commit splits utils.MakeSystemNode into three functions, making
creation of other node/service configurations easier. It also moves the
account manager into Node so it can be used by those configurations
without requiring package eth.