(1) Whether Article III permits the exercise of the judicial power of the United States by bankruptcy courts on the basis of litigant consent, and, if so, whether "implied consent" based on a litigant’s conduct, where the statutory scheme provides the litigant no notice that its consent is required, is sufficient to satisfy Article III; and (2) whether a bankruptcy judge may submit proposed findings of fact and conclusions of law for de novo review by a district court in a “core” proceeding under 28 U.S.C. 157(b).