refactor(config/init) add hooks to identity generation. useful for displaying messages to the user

@jbenet this commit re-introduces the peer identity line. It's very
useful. I understand it may have been removed because of the clashing of
the IDs. To alleviate this, this commit places some negative space
between the two lines.

'to test' -> 'to get started' as a stronger call to action

```
λ. ipfs2 init -f
initializing ipfs node at /Users/btc/.go-ipfs
generating key pair...done.
peer identity: QmWzjxNEYKjDAxuHJqvtLP1dZTDjreBSUsArWoHai1v9yP

to get started, enter: ipfs cat QmYpv2VEsxzTTXRYX3PjDg961cnJE3kY1YDXLycHGQ3zZB
```

License: MIT
Signed-off-by: Brian Tiger Chow <brian@perfmode.com>