* If a "tool" is also a raw material (e.g., as a "cow" is for producing milk),
be sure to add it to the inventory so that it shows up as one of the outputs
* Re-write the `computeMissingResources` method to be `craft` and refactor how
it performs calculations to be easier to follow, and to avoid several errors
in the prior calculation related to recipes which produce more 1 quantity of
the output items.
Andrew Miner