Replaced std::array by array
Replaced vec3 and mat3 by array<double, 3> and array<double, 9> respectively
Combined vec3.hpp and mat3.hpp into array.hpp
Renamed utility to safe_counter
Renamed utility to safe_counter
Added array.cpp
Replaced eq by zero
Renamed addition_task, subtraction_task, crossover_task to add, subtract, crossover