Update backpacks.conf

Updated to reflect newest Natura and Tinker's Construct additions.

New Natura wood products to Forester's. 

New Tinker's Barricades and Punji sticks to both Forester's (as wood products) and Hunter's (as befits makeshift walls and deadly spike traps). 

Tested against fresh 0.9.15b w/ all content mod addons to ensure compat.