Changed the ships in the code based on atlantisdev discussions.
The old style ships will still be used by the basic rule set.
Wargalleys, Knarrs, Barges, Triremes, Dromons and Carracks have
all disappeared; Zeppelins have been renamed.
Some changes were made to make importing data work a little more
cleanly, but these changes should ideally be applied to a fresh game.