accounts: fix data race when key is locked after the unlock timeout

Legalese updates

miner: fix current work data race

Fixed canary to require 2+ nonzero, not sum 2+

While here, also improve the docs and speed up the tests.
The tests used the scrypt keystore with ridiculous settins and took 20s
each.

xeth: fix #1485, data race in fiilter creation and event firing

cmd/ethtest, tests: add support for RLP JSON tests

miner: moved state sync

Travis container support

Decoding did not reject byte arrays of length one with a single element
b where 55 < b < 128. Such byte arrays must be rejected because
they must be encoded as the single byte b instead.

Moved the state sync so it only syncs the state when the block mining yield a possitive result

Prompt user to accept legalese when datadir doesn't exist

miner: smart mining

xeth: removed mutex lock

core: during chain reorg rewrite receipts and transactions

Work is now handled and carried over multiple sessions. Previously one
session only was assumed, potentially resulting in invalid (outdated)
work

* Larger work / result queue
* Full validation option

xeth: log signed tx hash

Added PutBlockReceipts; storing receipts by blocks. Eventually this will
require pruning during some cleanup cycle. During forks the receipts by
block are used to get the new canonical receipts and transactions.

This PR fixes #1473 by rewriting transactions and receipts from the point
of where the fork occured.

core: genesis preparation

Implemented the --genesis flag thru which we can set a custom genesis
block, including the official Ethereum genesis block.

core/vm: added str to op

accounts, crypto: fixed file naming for windows