Fix Naturalist Backpack dupe & delete bugs

Fixes Issue #64 and Fixes Issue #65
Both issues still occurred on the latest master branch.

No backpack is a ContainerNaturalistInventory, so it makes sense that it was a typo for ContainerNaturalistBackpack. 

Now Naturalist Backpacks do not pick up items while open, just like every other backpack. This fixes the above two linked issues, one which duplicates items one that deletes them.