Just 11 days after being named to preside over the trial of notorious gangster James “Whitey’’ Bulger, US District Court Judge Diane Casper said today she will not let her sudden arrival in the case push the long-awaited trial beyond its previously scheduled start date, June 6. “I do intend to keep’’ that date, Casper said from the bench today where she was overseeing wrangling between Bulger defense attorney J.W.