provide simpler core.IPFSNode constructor

[btc]

This is a common operation. We should provide a simple alias for it.

    // ~/.go-ipfs
    // IPFS_PATH
    ipfsPath, err := fsrepo.BestKnownPath()
    if err != nil {
        return err
    }
    repo := fsrepo.At(ipfsPath)
    if err := repo.Open(); err != nil {
        return nil
    }

    node, err := core.NewIPFSNode(context.Background(), core.Offline(repo))
    if err != nil {
        return err
    }

[whyrusleeping]

👍 I agree completely