IPNS fast resolution for content publisher

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.