Find multi-objective Pareto front using modified quicksort

This function returns the indices to a given matrix corresponding to the pareto optimal set of designs. The underlying algorithm of this function is based on quicksort, and similarly achieves an expected run-time of O(n lg n + n_p) for n designs (n_p of which are pareto optimal) with a favorable leading coefficient. Its implementation is vectorized where possible, and supports any data type defined under <,>,or min().