18 chain saw manuals added

18 more chain saw and pole saw manuals have been added recently:

- Earthquake: 1 chain saw manual
- Echo: 3 chain saw manuals, 4 chain saw parts lists
- Greenworks: 2 chain saw manuals
- Husqvarna: 1 pole saw manual, 4 pole saw parts lists
- Steeltec Commercial: 1 chain saw manual
- Tanaka: 1 pole saw manual, 1 pole saw parts list