Tweak trader offerings

• reduce uranium/phosphorite: 3 x 16 crushed of each seem a bit too much - could buy 96 of each in one trader run with 3 glass traders if I had enough gears
• add a tiny bit of phosphorite/uranium to pottery trader
• add woad/cornflower buying to potter trader
• add charcoal buying to glass trader
• add fired fireclay bricks buying to glass trader
• improve sell list of glass trader - he sells too much colored glass
• look at prices for colored crocks, apparently these sell for too much