Add rare Berry Bushes in Forest/Grassland

[Peter34]

Forest has surprisingly little food, apart from Bird's Nests which might randomly contain Eggs. Blueberries are very common in the Frozen biome, at least on the Navezgane mape (but I imagine they're common in random gen map too). I'd like these berry bushes to be very rare in Forest biomes and even rarer still in grasslands. But it'd just be nice if there was some food source that isn't hunting or looting Nests.