More mower and engine manuals added

Several lawn mower and engine manuals were added recently, for the following brands:

- Black & Decker: 1 lawn mower manual, 4 lawn mower parts manuals
- Honda: 1 lawn mower manual, 1 lawn mower setup guide
- Husqvarna: 1 lawn mower parts manual
- Kohler: 1 engine owner's manual, 2 engine parts lists