Manual Constructor of PointRange

[yushangdi]

It would be helpful if PointRange has a manual constructor, e.g. something like:

  PointRange(const size_t num_points, const unsigned int dims,
             const unsigned int aligned_dims, T* values)
      : n(num_points), dims(dims), aligned_dims(aligned_dims), values(values) {}

[yushangdi]

Also it would be helpful if size(), dimension() and ()[] are marked with const.