Fix player save data issue & multiple username implementations (#257)

* fix saving issue & multiple username implementations

* Update README.md

Updated the method for overriding in-game username from '-name' to 'username.txt'.

* remove unused include i forgot to get rid of while testing

Minecraft.Client/Windows64/Windows64_App.h

@@ -33,6 +33,7 @@ public:
 	virtual void TemporaryCreateGameStart();
 
 	bool m_bShutdown;
+	wstring g_playerName;
 };
 
 extern CConsoleMinecraftApp app;