Closes#2421.
I am of the opinion that the spec is easier to read than this though,
and we shouldn't really explain this here other than that we use a variant
of station to station protocol, with X25519 for the diffie hellman, and we
describe the related security properties.
* addr_book_strick=false on local nets
* link to spec
* spec: remove TODO, see #1749 instead
* spec: make issues from TODOs
* update docs on addr_book_strict option
ValarDragon
Zach
Peng Zhong