feat(daemon) `ipfs daemon --initialized`

With this PR, users can fetch and run ipfs in _one_ command.

```
docker run -d -p 4001:4001 -p 5001:5001 jbenet/go-ipfs daemon --initialized
```

Magic.

nb: needs https://github.com/jbenet/go-datastore/pull/9
In general, i'm sketched out by static `init` functions. Is there a way to avoid this? Not a big deal but I'd feel more comfortable with an explicit initialization in client libs. Or, are these sane defaults that should always be set?