Acorns

Adds Acorns as a food source.

Also adds a Wooden Mallet which is needed to crack the Acorn shells.

Acorns drop from Oak tree leaves and are highly nutritious. 
Acorn flour is gluten-free. It must be mixed with another flour and water to make bread dough.
It gives a 50% nutrition boost to bread.

Also adds Acorn Griddle Cakes. These can be made without adding another flour.

Acorns can also be fed to pigs.

"There is no food that means more to me than the acorn, for the acorn fulfills both a promise and a fantasy: that the forest will provide for me. When I gaze across the [valley] I see more than scenery. I see thousands of acres of bounty, millions of pounds of delicious food dropped from the crowns of countless trees, waiting to be gathered by eager hands. I see more food than I could ever eat—more than I can even fathom. A wilderness and an orchard in one."
...from "Nature’s Garden: A Guide to Identifying, Harvesting, and Preparing Edible Wild Plants" by Samuel Thayer.