Feature: bootstrap_mode

[rauljim]

Take some of the code from the 'investigate_traffic' branch and merge it into mainline.

The idea is that a main bootstrap node should avoid being added to other routing tables to reduce incoming traffic. The approach, so far, is to:

• ignore ping queries
• reply to one find_node query per IP per hour ??doublecheck
• reply to every get_peers queries with no token
• ignore announce_peer queries