12 more lawn mower manuals added

Links to 12 more lawn mower manuals and parts lists were added to the site recently:

- Bad Boy: 1 mower manual, 1 mower setup manual
- Great Dane: 1 mower manual
- Husqvarna: 1 mower manual, 2 mower parts manuals
- Poulan: 1 mower manual, 1 mower parts manual
- Poulan Pro: 1 mower manual, 1 mower parts manual
- Snapper: 2 mower manuals