Balancing - Mining materials exports

[courierbravo]

Added the ability to sell off your mining materials for profit. All prices are relatively low, so it shouldn't mess up the balance of things too much. Consequentially, engineering can now sell its gold, silver, and platinum to operations. Also, I removed market elasticity from this materials list. Just to make things far more consistent, and remove any potential and needless frustration. Thank you to @BoomerThor for helping me through this!