* EffectPlayer : Added use of "CreateInstance()" to get an instance of a sound effect
  that can be stopped for looped sound effects.
* EffectPlayer : Added code for the control methods when the sound effect instance is in use.
* SimpleAudioEngine : Added management of looped sound effects and a method to stop all
  running looped sound effects.
* MusicPlayer : Added some defensive code around SaveMediaState.