A woman who has been central to R. Kelly’s legal troubles for more than two decades testified Thursday that the R&B singer sexually abused her “hundreds” of times before she turned 18 years old, starting when she was 15.Jane — the pseudonym for the now 37-year-old woman at Kelly’s trial on child pornography and obstruction of justice charges — told jurors that in the late 1990s when she was 13, she asked the Grammy award-winning singer to be her godfather because she saw him as an inspiration and mentor.She said within …