Added Gui option to filter out 0 stock items
Fixed percent increase if stock at 0 not applying to total price.
Added cool-down option in config to buy/sell
Added per item overrides
the following options now exist
base: 100.0 #price price
min-stock: 50.0 # Pricing curve will act as if 50 is the "0" point
max-stock: 1000.0 # Pricing curve "full" point
min-stock-storage: 10 # Buying will convert to partial/fail below 10 stock
max-stock-storage: 2000 # Selling will fail above 2000 stock (hard limit)
disable-buy: false #disable buying
disable-sell: false #disable selling