FoodData Central: do we want to remove records where nutrientAmount is 0?

[colleenXu]

In ~22% of the dataset (1294 / 6011 records), the nutrient wasn't actually found in the food (object.nutrientAmount = 0). I'm not sure if we want to keep this info or not - since it means there WASN'T a relationship found between the nutrient and the food.

It's not an issue for BTE use because I am using the BioThings filter parameter to only retrieve records with amount > 0.
(based on biothings/biothings_explorer#683 (comment))

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I previously brought this up in #170 (comment) but it wasn't addressed.