Introduce tooling to monitor network health

In order to respond to any problem with the neptune network in a timely manner, we need to know how it is doing. Some important metrics include:

• difficulty over block height
• number of blocks over time
• number of nodes over time
• mempool size over time
• orphan rate over block height
• composer & guesser time (respectively) over block height (if such data can be obtained)
• visualize the chain and all its forks as a graph, hovering a node gives node info
• re-organizations, and info related to them

I have never developed one, but like the look & feel of grafana dashboards.