Change AI name to ""
Merge branch 'gamelogic' of https://github.com/xvblack/Tetris-se2013 into gamelogic

Conflicts:
	Tetris/AchievementSystem.cs
	Tetris/AdvancedGUI/DualModePage.xaml.cs
	Tetris/AdvancedGUI/GameModeSelectionPage.xaml.cs