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
The issue is clarity and sound composition. The composer being "owned" by the composed is peculiar.

The predominant justification for delegating the composer's Close to the context closer seems to be the sync.Once guarantee. This seems insufficient, since thread-safety is ultimately the responsibility of _clients_ of the Node. 

Sharing memory without synchronization and passing objects without explicit ownership is a client problem and serves as an indication of other issues.