Expose DC usage in a graphable format

[allenan]

We'd like to be able to graph DC usage over time. Maybe this could be modeled after the rewards/stats endpoint format?

[madninja]

@allenan

1. does that mean we could get rid of it in the root /stats endpoint? It would actually help performance of that endpoint a lot
2. would you expect dc usage to be bucketed the same way as the proposed rewards/stats endpoint in #142?

[allenan]

@allenan

1. does that mean we could get rid of it in the root /stats endpoint? It would actually help performance of that endpoint a lot

We could do that if it really helps performance. We use that in the explorer, but could switch over to the new endpoint for the summary stats

2. would you expect dc usage to be bucketed the same way as the proposed rewards/stats endpoint in #142?

If it's easy to follow that same pattern, I think those stats would be helpful if bucketed by Hotspot. In the sense that we could understand how much DC the median hotspot is transferring