ADD sudoku::find_cell_value_by_exclusion

Add two subfunctions that it calls

Add argument parser for calling find_cell_value_by_exclusion or the
original find_feasible_values

Revive the function solve_sudoku_simplistic

It seems that combine solve_sudoku_simplistic with solve_sudoku (should
rename to recursive) has the best results (all 21 puzzles solved in
fastest time)

Code requires cleanup!