take a db backup on first execution to speed up future runs

Installing sample data and then doing a normal installation (equivalent to upgrading magento from 1.2) can take a little bit. To speed this process up, if you do this a lot of times, this patch will take a snapshot of the freshly installed Magento instance and saves the database sql along with the config.xml file (because of the encryption key) for reuse on subsequent runs.

The use of this feature is optional through 
backup.target       =