PORT ALLEN — A Port Allen bar is marking more than a century in business, and the family behind it says they have no plans to stop.Jack's Place opened in 1924 by Jack Saia, a first-generation American who immigrated from Sicily.Now, his great-grandchildren are the third generation keeping the bar running."We are probably the oldest business in Port Allen, maybe even in West Baton Rouge Parish," Jill Saia says. "I remember the busiest we've ever …