Modifications to PokerSimulator and other refactorings.

- Modified PokerSimulator to allow instances to simulate more than once
- Updated TexasPoker and TexasTourney with new PokerSimulator usage
- Reduced scope of some local variables in TexasPoker
- Created showShowdown() in TexasPoker
- Updated getNumCanBet() in TexasPoker
- Modified clean-up for-loop in endRound() of all games