Dump and restore smartbch

re: #22

To make a dump (make sure the donor smartbchd is stopped)

```bash
sudo tar --exclude=priv_validator_state.json --use-compress-program=pigz -cvf /tmp/smartbch.tar.gz -C data/smartbchd data
```

To restore (make sure the recipient  smartbchd is stopped and clean)

```bash
sudo tar --use-compress-program=pigz -xvf  /tmp/smartbch.tar.gz -C data/smartbchd/
```