p2p/discover: sha3-based node distance

core: transaction pool fixes & resending transactions

Ethash reloaded

jsre: support for setTimeout, sendAsync 

The previous metric was pubkey1^pubkey2, as specified in the Kademlia
paper. We missed that EC public keys are not uniformly distributed.
Using the hash of the public keys addresses that. It also makes it
a bit harder to generate node IDs that are close to a particular node.

added and eval queue for serializing JSRE vm execution

cmd/geth: colorize console output in windows

eth, eth/downloader: error handlers and td checks

If a peer fails to respond (disconnect, etc) during hash downloading
switch to a different peer which has it's current_hash in the queue's
peer set.

The downloader is no longer responsible for processing blocks. The
eth-protocol handler now takes care of this instead.

Added graceful shutdown during block processing. Closes #846

Conflicts:
	p2p/server_test.go