Backup improvements as mentioned in https://github.com/agehret/asino/issues/24

- create backup directory if it doesn't already exist.
- warn user if mysqldump isn't installed, and disable creating backups.
First stab at catgories with subcategories
Merge pull request #25 from phillipoertel/upgrade

Backup improvements as mentioned in https://github.com/agehret/asino/iss...