Update install script to Confluence 5.5.6

Signed-off-by: Gianpaolo Macario <gmacario@gmail.com>
Merge pull request #15 from gmacario/update-confluence-556

Update install script to Confluence 5.5.6
Prepare restore of CONFLUENCE_BACKUP

Signed-off-by: Gianpaolo Macario <gmacario@gmail.com>