Create 19_Permutations.cs

19. Write a program that reads a number N and generates and prints all the permutations of the numbers [1 … N].
   Example: n = 3 -> {1, 2, 3}, {1, 3, 2}, {2, 1, 3}, {2, 3, 1}, {3, 1, 2}, {3, 2, 1}