fault detection and stats collection in live overlay (opt-in only)

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Problem: understanding the health, bugs and faults in deployed P2P software is hard
Goal: use a package with wide usage that solves this, instead of our own custom code.

Only enable with user consent (plus enabled by default in test releases).

Backend: http://graphite.wikidot.com/
Network deamon: https://github.com/etsy/statsd
Python wrapper: https://github.com/WoLpH/python-statsd/

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Finding a bug is all about reproducing it in the lab.

We usually are not even aware what can go wrong. The easy bugs appear in our standard unit tests. They get removed. The hard ones remain. Ongoing epic effort.