Insert the skeleton of the second game.

Because of a lack of imagination, we call it pong (because what's ping without pong).
Create the pong game.

* Move & adapt some of the ping functions to use in common with pong.
* Create placeStars & placeOneStar function, used by pong game.
* Create setPong & playPong function
Finish Pong game

* Fixed a missing return from place stars function
* Fixed missing cast to int for user input
* isPongGameWon function is now verbose
* Fixed playPong() function (was calling playPing() instead of playPong())