Expose IP:port of the peer that announced a new block

[sesam]

The idea being, if you can ask the node that is first to know about a block, you should peer with either that node, or one of it's closest peers.

If you also can get to know the ip:port of a node that is much slower at getting that block, then you could on purpose place your newly spun up, but reliably hosted node, as a go-between and connect to both of these, making the gossip network scale better as a result.