Add script do-extract-backups.sh

This is an example (to be customized) of how to extract Confluence and JIRA backups
from either a tarball or a Clonezilla image.

Signed-off-by: Gianpaolo Macario <gmacario@gmail.com>
Add more options and comments

Support extracting backups from a remote server
Extract backups to DESTDIR
Add usage explanations and known limitations

Signed-off-by: Gianpaolo Macario <gmacario@gmail.com>
Some more cleanup
Merge pull request #18 from gmacario/do-extract-backups

Add sample script for extracting Confluence and JIRA backups