Support underclocking and overclocking in optimization queries

It would be nice if a query could say "from exactly 6 smelters" even if an optimal setup only needed 5. Doing so would produce a result with 6 underclocked smelters. Likewise, supporting overclocking in the same way.

Right now, this is a pretty complicated change to makes. All of the equalities being added to the inputs are less than or equal to relationships, so the optimizer will always use the exact number of smelters needed. I think we would need to add some new variables to the optimizer to allow under/overclocking every recipe. That way, the large equality for a single item would use these under/overclocking values as coefficients on each recipe.