Kurt Cobain’s widow Courtney Love once demanded that the entire police file on his death be handed over to her, with no copies left at the Seattle Police Department, according to a newly unearthed document. The Nirvana frontman’s widow made the stunning request Oct. 20, 1995 — about a year and a half after her 27-year-old musician husband was found dead with a gunshot wound to the head in a greenhouse at their Seattle mansion. Investigators had declared Cobain’s death a suicide from the outset, a conclusion Love concurred with — but a group of researchers who believe it was…