core/types, ethclient: fix broken subscriptions

ethereum, ethclient: add SyncProgress API endpoint

cmd/evm, cmd/geth, cmd/utils: move version handling to cmd/utils

miner: Prevent attempts to close nil quit channel in agent (fixes #2948)

Transaction pool optimizations

contracts/ens: Replace setOwner with setSubnodeOwner per EIP137

swarm: plan bee for content storage and distribution on web3

Small docker run example for main README

This change imports the Swarm protocol codebase. Compared to the 'swarm'
branch, a few mostly cosmetic changes had to be made:

* The various redundant log message prefixes are gone.
* All files now have LGPLv3 license headers.
* Minor code changes were needed to please go vet and make the tests
  pass on Windows.
* Further changes were required to adapt to the go-ethereum develop
  branch and its new Go APIs.

Some code has not (yet) been brought over:

* swarm/cmd/bzzhash: will reappear as cmd/bzzhash later
* swarm/cmd/bzzup.sh: will be reimplemented in cmd/bzzup
* swarm/cmd/makegenesis: will reappear somehow
* swarm/examples/album: will move to a separate repository
* swarm/examples/filemanager: ditto
* swarm/examples/files: will not be merged
* swarm/test/*: will not be merged
* swarm/services/swear: will reappear as contracts/swear when needed

contracts/release: move package release to contracts/

contracts/ens: regenerate binding with solc v0.3.6

contracts/chequebook: fix possible reentrancy bug in chequebook contract

Godeps: update golang.org/x/...

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.

contracts/ens: Add ENS contract binding

contracts/chequebook: add chequebook contract wrapper

The wrapper code is adapted from the swarm/services/chequebook package
with the following mostly cosmetic changes:

* The code now uses the new Go API interfaces to query balances. Some
  minor functional changes were required to make this work.
* The package no longer depends on swarm/services/swap/swap. References
  to swap.Promise are replaced by interface{}, the base type of Promise.
  This is temporary.
* The contract wrapper has been regenerated with latest abigen
  and solc v0.3.6.
* There is a new generator that creates the 'deployed code' variable.
* Documentation comments now follow the recommended godoc style.
* [CHEQUEBOOK] log prefixes are gone.
* LGPL license headers have been added to all files.

Also remove the now un-needed mutex locking in Start() and Stop()

Stable Go API, part 1

internal/ethapi: Fix bug in opCodeWrapper usage

internal/ethapi: Improve tracer error reporting and serialization