19 lawn mower manuals, parts lists, and service bulletins added

19 more mower manuals and other pieces of documentation have been added recently, for the following brands:

- Briggs & Stratton: 2 bad links fixed

- Black & Decker: 1 lawn mower manual, 11 lawn mower parts lists

- Craftsman: 1 lawn mower manual

- Troy-Bilt: 1 lawn mower service bulletin

- Weed Eater: 2 lawn mower manuals, 2 lawn mower parts lists, 1 lawn mower service bulletin, 4 bad links fixed