Quantity
In order to be able to convert between, say, Imperial and Metric down the line, we separate Quantity and Units. So for example, if you want 1/2 teaspoon, the Quantity is "1/2", and the Unit is "tsp".
Quantity is intentionally a text field. Ideally, you should put a number of some sort here, but if the correct value is "a few", say that. (We'll figure out how to parse that later.)
