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

Queries now can be cancelled and the resources collected

ipfs blocks local returns _all_ local refs. For now this is one
long op. future commits will make it async.

fix listener problems