dht find connected peers

This PR extends the DHT to send information re: peer "connectedness".
This means that --upon resolving dht queries -- connected peers will
signal whether or not they are directly connected to the peer. this is
in preparation for mesh messaging, and our "STUN" for NAT traversal.
yeah. functions like those are kosher :+1: 

given the existence of those functions, i don't see a reason to rely on the enum value to provide a mapping between the types. `iota` seems like an all-around better deal.

but it's really not a big deal. i don't forsee a bug being introduced due to the decision. :evergreen_tree: :fist: : :evergreen_tree: 

Looking at the big picture, where would you want me to focus CR attention? Is there anything particular you're concerned about?

(It's easy to get lost in syntax)