GitLab

This commit adds an option to turn off all encryption. This is a mode
used for tests, debugging, achieving protocol implementation interop,
learning about how the protocol works (nc ftw), and worst case
networks which _demand_ to be able to snoop on all the traffic.
(sadly, there are some private intranets like this...). (We should
consider at least _signing_ all this traffic.)

Because of the severity of this sort of thing, this is an
all-or-nothing deal. Either encryption is ON or OFF _fully_.
This way, partially unencrypted nodes cannot be accidentally left
running without the user's understanding. Nodes without encrypted
connections will simply not be able to speak to any of the global
bootstrap nodes, or anybody in the public network.

License: MIT
Signed-off-by: Juan Batiz-Benet <juan@benet.ai>