IPFS DHT integration - Githubissues

Wherein we take the firsts steps to integrate with IPFS:

Refactors mcnode/proto to extract network related functionality
Integrates libp2p-kad-dht and connects to the DHT as a client, with bootstrap through the IPFS planets; leeching ok for now per jbenet.
Node.doLookup is modified to use the DHT for looking up peers as a fallback to directory lookup (or when there is no directory), and also caches lookup results with the standard peerstore ttl
Fixes peer api operations to fail consistently with 404 when there is a peer lookup failure.
Adds a /net/lookup/{peerId} endpoint to perform network lookups for debugging purposes

Closes #81

Example of node discovery through DHT:

$ mcclient listPeers
QmeiY2eHMwK92Zt6X4kUUC3MsjMmVb2VnGZ17DhnhRPCEQ
QmSp4R1R3rk7ho8M6P24sQG2yFiz8THYjwei468sz3GbSM
QmTVsocFCSEdPyM8dZ734GRhjvvmYyL9fShyezVkbPj17E
QmZ6dckUhRouVr6AsBTpK6vMLVpcz1KAeJAJVQEZQ5gCek

# DHT lookup!
$ curl http://localhost:9002/net/lookup/QmSbgwkKxtrBFDoGGwoKqH7soYiL64xpMK5oEYdiRnQGJp
/ip4/10.10.1.191/tcp/9001
/ip4/54.242.130.109/tcp/9001

$ mcclient id QmSbgwkKxtrBFDoGGwoKqH7soYiL64xpMK5oEYdiRnQGJp
Peer ID: QmSbgwkKxtrBFDoGGwoKqH7soYiL64xpMK5oEYdiRnQGJp
Publisher ID: 4XTTMGkYEx5trQX5VV32S82gguRMtVFQL5UDnZNHzyNEHKBeZ
Info: Mediachain Labs test node

mediachain / concat

IPFS DHT integration #90