[1.0.2059] Bills: select source stockpile

[shentino]

You should be allowed to specify what stockpile a work bill should pull its ingredients from.  The ingredient radius thing is nice, but its fixed shape (a round circle) interferes with my freedom, and if I want to retain flexibility it interferes with an "industrial" layout of packed kitchens that have specialties.

For example, it would make it much simpler to implement a "feed stockpile" by plopping a stockpile square right in front of the stove and then picking it as the stove bill's input.