dht: changed msgs, include multiple addrs + conn type

See https://github.com/jbenet/go-ipfs/issues/153#issuecomment-63350535
dht tests: dont introduce nil multiaddr

this is the type of assumption we shouldn't violate.
net: add Connectedness var.
dht/pb: changed PeersToPBPeers to set ConnectionType

Uses an inet.Dialer
net: add LocalPeer funcs
dht: update to use net.LocalPeer
dht: FindPeersConnectedToPeer