Rename the "getBest..." methods to "getWinning..."

[LarsGast]

The method PokerHand.getBestHand() already exists to get the best hand based on a list of cards. The PokerHand.getWinningHand() method gets the winning hand among a list of PokerHands. This method calls other methods with names like getBestStraightFlush() and getBestTwoPair(). For consistency, these methods should be called getWinningStraightFlush() and getWinningTwoPair().

Since these methods are private, the interface of the NuGet package will not change.