UPDATE, 10:38: The first of the M-8 cars is on its way to Grand Central after leaving Stamford station. 10:00: This report filed by Martin Cassidy: STAMFORD &ndash; The long-awaited debut of Metro-North&rsquo;s M-8 rail cars took place this morning at 10:30 a.m. The first of the six-car trains left Stamford at 10:30 and is [...]