core/vm: add limit option to LogConfig

all: remove weird files

cmd/utils, core, params: explicitly pick reprice fork for fast sync

whisper: project restructured, version 5 introduced

This commits adds a draft version of the new shh v5 protocol.
The new version is not on by default, --shh still selects version 2.

* cmd/evm: Allow stdin and files as sources of bytecode

* cmd/evm: Print and exit instead of panicing

* cmd/evm: fix compile and vet errors

This commit includes several API changes:

- The behavior of eth_sign is changed. It now accepts an arbitrary
  message, prepends the well-known string

        \x19Ethereum Signed Message:\n<length of message>

  hashes the result using keccak256 and calculates the signature of
  the hash. This breaks backwards compatability!
  
- personal_sign(hash, address [, password]) is added. It has the same
  semantics as eth_sign but also accepts a password. The private key
  used to sign the hash is temporarily unlocked in the scope of the
  request.
  
- personal_recover(message, signature) is added and returns the
  address for the account that created a signature.

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.

Fixes #3203

Update goleveldb, add debug.chaindbCompact

eth/downloader: fix a data race in a log output

cmd/geth, code, eth/downloader: tune import logs and mem stats

cmd/geth, trie: report on trie cache unloads, also add debug log

cmd, core/state: allow configurable trie cache generations

core/vm: fix GASPRICE string (resolves #2553)

trie: improve cache unloading mechanism

cmd/geth, trie: track and report trie cache misses

The pending state was not copied while not mining, leading to a data race.

core: Add block processing time metric collection

cmd/geth: compact and print database stats after an import

common, core, eth/downloader: adjust import log formatting

This was caught by the new invariant check.