IPNS fast resolution for content publisher

[aschmahmann]

Given that IPNS is basically designed to fail with multiple writers I think it's reasonable to assume that if you have an IPNS private key stored locally and you do ipns name resolve myKey it should just immediately return the local data if you have it available (i.e. not even bother with a network request).

I think this is true even if you pass the --stream option, although I'm open to other opinions.

If for some reason you've decided that you're going to reuse an IPNS private key across multiple machines we can either use a new flag (or piggyback on the -n flag) to let force a network search.

Thanks @lidel, @Stebalien, @djdv for help fleshing this out.