Update CONFLUENCE_INSTALLFILE to 5.5.3

Signed-off-by: Gianpaolo Macario <gmacario@gmail.com>
Update CONFLUENCE_BACKUP to latest

Signed-off-by: Gianpaolo Macario <gmacario@gmail.com>
Merge pull request #7 from gmacario/update-confluence

Update Confluence to version 5.5.3