p2p/net/swarm: fix connect self problems

This adds two checks after a successful conn.Dial
* if the remote peer is not who we wanted, close conn
* if the remove peer is outselves, close conn

(the second is redundant, but the codebase may evolve to
end up disabling the first check, so keeping the second
in place helps)

note:
Loopback addresses are actually sent out (they _have to be_,
in cases where there are >1 node in the same machine), so
many times when trying connections, nodes end up dialing
themselves.

dont send ip6 link local addrs

use conns to enumerate peers for network diagnostic

cc @whyrusleeping

Gateway Server

replaced H
moved internal errors into function.
Signed-off-by: Simon Kirkby <tigger@interthingy.com>

adds
 trailing slash redirection
 index.html return
 templated directory listing

Signed off : Simon Kirkby <tigger@interthingy.com>

ds-query + ipfs refs local

the prefix should be as short as possible, as this is a
per-block overhead.

@mappum would this work?

cc @mappum can we do this for the copyChunks case?

using Header().Set after WriteHeader() has no effect.
cc @mappum