WILTON - Gov. M. Jodi Rell was in Wilton Tuesday to mark the start of an upgrade for Metro-North's Danbury line.The entire line, 24 miles from Norwalk to Danbury, will be upgraded at a cost of about $53 million, more than $30 million coming from the federal government.Governor Rell says it will mean better, safer and more reliable service for commuters in communities. Among the improvements will be replacing the old-fashioned, manually operated signal system with a modern, remote-controlled system.