Jack Welch was a railroad conductor’s son who rose to chairman and CEO of General Electric.During the 20 years he led the conglomerate, its market value grew from $12 billion to $410 billion.Fortune magazine once called him “manager of the century,†but he also was known as “Neutron Jack†for slashing tens of thousands of jobs.  Jack Welch, a railroad conductor’s son who became chairman and CEO of General Electric and led it for two decades, growing its market value from $12 billion to $410 billion, has died. He was 84.His death was announced Monday by his wife, Suzy. With...