v1.0.1 - small bug fix release

Most of my recent work has been refactoring the code to make future enhancements easier. However, I did manage to fix a few small bugs:

• Buying and selling high-priced goods could result in a negative buy/sell price if the price exceeded a 2-byte integer.
• Selling equipment at a port that doesn't carry that equipment did not give the player any money back.
• Buying a new hull didn't immediately change the image of the ship in the starfield.