wishlist: way to ensure ipfs daemon is running

When building things on top of the ipfs cli, such as the git-annex integration, it would be useful to have a command that makes sure the daemon is running, starting it up if not, and exits 0 once the daemon is running. This way if the user forgot to start the daemon, ipfs can still be used by the thing built on top of it.

It would be especially nice if the command blocked until the daemon had gotten bootstrapped enough to the DHT that requests for objects were likely to start to succeed.