Authorizing, under certain circumstances, a personal representative to petition the orphans' court to interpret a decedent's will in accordance with the decedent's intent as demonstrated by certain extrinsic evidence; establishing a certain rebuttable presumption as to a decedent's intent; authorizing the personal representative to require a certain legatee to demonstrate the use of a legacy under the decedent's will; requiring the court to interpret a will in a certain manner if certain language is included in the will; etc.