Make peers persistent

[msolefonte]

To prevent peers from losing their data after a failure or restart, I strongly recommend to add persistence in them by storing the data under /var/hyperlegder/production (blockchain) and under /opt/couchdb/data (world state) in EBS volumes.

Making Wold State persistent too would allow organizations to have secret transactions without involving the blockchain.

I do not know how much storage should be required in EBS (perhaps 200GB for each one, as with Kafka), but I would recommend to set that as variables in env.sh and let the user set them.

As I said in another issues, this is simple to do, I can send the PR if this issue is approved, but it has to be reviewed by another one.

[msolefonte]

Pull Request #12 has been created