(ctor) GainSkillObjectiveInstance( GainSkillObjective objective, MLQuestInstance instance )
      GainSkillObjective Objective( get; set; )
      bool Handles( SkillName skill )
      virtual bool IsCompleted()
      virtual void OnQuestAccepted()
      virtual void OnQuestCancelled()
      virtual void OnQuestCompleted()
      virtual void WriteToGump( Gump g, ref int y )