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

This commit changes the discovery protocol to use the new "v4" endpoint
format, which allows for separate UDP and TCP ports and makes it
possible to discover the UDP address after NAT.