How to detect and repair faults

- Moved draft-ietf-p2psip-diagnostics and draft-ietf-p2psip-self-tuning
  to normative references.
- Moved Section 3.6.3 to 5.5 and expanded the text.
- -diagnostics is mandatory to implement for 10^5+ nodes overlays and
  recommanded for all.
- -self-tuning is recommanded for all overlays.

Bug: deanwillis/p2psip-base-master#13
Bug: deanwillis/p2psip-base-master#134