Revert "Project modernization (#630)"

This code was not tested and breaks in Release builds, reverting to restore
functionality of the nightly. All in-game menus do not work and generating
a world crashes.

This reverts commit a9be52c41a.

Minecraft.World/MemoryLevelStorageSource.cpp

@@ -29,7 +29,7 @@ void MemoryLevelStorageSource::clearAll()
 
 LevelData *MemoryLevelStorageSource::getDataTagFor(const wstring&  levelId)
 {
-	return nullptr;
+	return NULL;
 }
 
 bool MemoryLevelStorageSource::isNewLevelIdAcceptable(const wstring&  levelId)