Method SummaryColumn

Bcore/src/main/cpp/Dobby/tests/catch.hpp:11979–11980

struct SummaryColumn {

  SummaryColumn(std::string _label, Colour::Code _colour) : label(std::move(_label)), colour(_colour) {
  }
  SummaryColumn addRow(std::size_t count) {
    ReusableStringStream rss;
    rss << count;