Draw Histograms using peers' data

[Svedrin]

child of #40

I'd like to be able to draw histograms where a node's own data is included, and the data from its peers, so that I can easily compare the two.

For that, a node probably needs to store which of its peers it sent a target to, so that it knows which peers to query. Or do we just not care and just query all the MESHPING_PEERS, because who else could it be? I need to think about this.