Fix save list, delete save, exit without saving, and blank username on Windows64 (#539)

* Fix world save rename not applying new name

KeyboardCompleteWorldNameCallback had no _WINDOWS64 branch, so the
typed name was validated then silently discarded on every rename attempt.

Write the new name to a worldname.txt sidecar file next to the save
(Windows64\GameHDD\{folder}\worldname.txt) and update the in-memory
display name immediately. ReadLevelNameFromSaveFile now checks for this
sidecar first so renamed saves persist correctly across restarts.

* Fixed gamertag being blank upon renaming and re-joining a save

* Save deletion fix, exiting without saving fix

* Add native in-game keyboard UI for world naming and renaming

Minecraft.Client/Common/UI/UIScene_CreateWorldMenu.h

@@ -51,6 +51,12 @@ private:
 	DLCPack * m_pDLCPack;
 	bool m_bRebuildTouchBoxes;
 
+#ifdef _WINDOWS64
+	bool m_bDirectEditing;
+	wstring m_worldNameBeforeEdit;
+	int m_iDirectEditCooldown;
+#endif
+
 public:
 	UIScene_CreateWorldMenu(int iPad, void *initData, UILayer *parentLayer);
 	virtual ~UIScene_CreateWorldMenu();