Sigma Systems announced Monday that it has received a major investment from Birch Hill Private Equity Partners Management Inc. Sigma, which provides subscriber-management software, said in a press release said the new partnership between Sigma and Birch Hill will significantly improve product development plans and create advanced solutions for their customers. “Sigma’s strength is in the deep industry knowledge of our people and its firm commitment to product innovation that our customers have come to expect from us,” Sigma CEO Tim Spencer said in the release....