"If you build it, they will come."That advice, which prompted an Iowa farmer in the 1989 movie "Field of Dreams" to plow over his corn field and build a baseball diamond, has become the mantra of many high-tech startups promoting electronic commerce on the Internet. And the cruise travel industry has also embraced this “shop by computer” concept.Indeed the Internet can be a wonderful source of information to help you plan an exciting holiday, obtaining ship and stateroom descriptions, itinerarie.