Last October, Brynn Berkowitz’s fifth grade extra-credit math assignment involved graphing her large Halloween candy haul. The school math challenge spurred Brynn and her father, David – who has an interest in computer programming – to create an app called “Haullo,” which adults and kids can download to turn trick-or-treating into an interactive game. Brynn, now 11, lives in Needham and is a sixth grader at The Rashi School, a