BaseAttributes
      (ctor) BaseAttributes( Item owner )
      (ctor) BaseAttributes( Item owner, GenericReader reader )
      (ctor) BaseAttributes( Item owner, BaseAttributes other )
      bool IsEmpty( get; )
      Item Owner( get; )
      int GetIndex( uint mask )
      int GetValue( int bitmask )
      void Serialize( GenericWriter writer )
      void SetValue( int bitmask, int value )