DETROIT — E-mails showing that General Motors ordered a half-million replacement ignition switches nearly two months before telling the government of a safety recall will be heavily scrutinized by federal prosecutors who are investigating GM’s conduct, according to legal experts. The e-mail chain, released Monday by an attorney suing GM, again raises questions about how forthcoming GM has been with safety regulators and lawmakers as well as a GM-funded investigation into the defective switches by former U …