Add basic scripts to install/uninstall debian init.d scripts 

Scripts to install an init.d script for starting the Spark server on boot. Fixes [issue 17](https://github.com/spark/spark-server/issues/17)

Usage (from `<spark-server-root>/js`): 

```
sudo ./install-init-d.sh
```

To uninstall:

```
sudo ./uninstall-init-d.sh
```

The user can then start/stop the server manually by using:

```
sudo /etc/init.d/sparkup start <or stop>
```

Logs are directed to files in `/var/spark`