Add a new Saltpetre recipe because industrial amounts are unpleasant to make

[RGBDeadSilent]

You can already frequently buy 600u of Saltpetre from cargo via Weed Froggo. Thats easily 1,800u of Black powder. That is a lot of explosives to ruin the station with if you build it right. So... Already easy to get, its a key explosive reagent so maybe no on making it easier to get.