message: Use std::accumulate instead of for loop product
diff: #include <utility>
  #include <stdexcept>
  #include <cstddef>
  +#include <numeric>
  namespace Gudhi {
  @@ -738,11 +739,9 @@ template <typename T>
  void Bitmap_cubical_complex_base<T>::setup_bitmap_based_on_top_dimensional_cells_list(
  const std::vector<unsigned>& sizes_in_following_directions, const std::vector<T>& top_dimensional_cells) {
  this->set_up_containers(sizes_in_following_directions, true);
  -
  - std::size_t number_of_top_dimensional_elements = 1;
  - for (std::size_t i = 0; i != sizes_in_following_directions.size(); ++i) {
  - number_of_top_dimensional_elements *= sizes_in_following_directions[i];
  - }
  + std::size_t number_of_top_dimensional_elements = std::accumulate(std::begin(sizes_in_following_directions),
  + std::end(sizes_in_following_directions), 1,
  + std::multiplies<unsigned>());
  if (number_of_top_dimensional_elements != top_dimensional_cells.size()) {
  std::cerr << "Error in constructor Bitmap_cubical_complex_base ( std::vector<unsigned> "
  << "sizes_in_following_directions, std::vector<T> top_dimensional_cells ). Number of top dimensional "
  @@ -770,13 +769,10 @@ void Bitmap_cubical_complex_base<T>::setup_bitmap_based_on_vertices(const std::v
  std::vector<unsigned> top_cells_sizes;
  std::transform (sizes_in_following_directions.begin(), sizes_in_following_directions.end(), std::back_inserter(top_cells_sizes),
  [](int i){ return --i;});
  -
  this->set_up_containers(top_cells_sizes, false);
  -
  - std::size_t number_of_vertices = 1;
  - for (std::size_t i = 0; i != sizes_in_following_directions.size(); ++i) {
  - number_of_vertices *= sizes_in_following_directions[i];
  - }
  + std::size_t number_of_vertices = std::accumulate(std::begin(sizes_in_following_directions),
  + std::end(sizes_in_following_directions), 1,
  + std::multiplies<unsigned>());
  if (number_of_vertices != vertices.size()) {
  std::cerr << "Error in constructor Bitmap_cubical_complex_base ( std::vector<unsigned> "
  << "sizes_in_following_directions, std::vector<T> vertices ). Number of vertices "
  