DataAsset blueprints have the wrong NativeClass

UDataAsset's constructor assumes itself to be the native class, and caches that value for use by the asset registry. However, if the data asset type is defined in a blueprint (i.e. subclassing UPrimaryDataAsset), the NativeClass will incorrectly display as a blueprint class.

Initially proposed fix is to iterate up the parent chain until a native parent is found:

UClass* MostDerivedNativeClass = GetClass();
while (MostDerivedNativeClass)
{
	if (MostDerivedNativeClass->HasAnyClassFlags(CLASS_Native | CLASS_Intrinsic))
	{
		// Found native class
		break;
	}
	else
	{
		MostDerivedNativeClass = MostDerivedNativeClass->GetSuperClass();
	}
}
NativeClass = MostDerivedNativeClass; 

However, this could be further improved to store the registry tag at save time and avoid adding data to the asset itself.

1. Create a blueprint MyDerivedDataAsset that subclasses UPrimaryDataAsset
2. Create a Data Asset of type MyDerivedDataAsset
3. Hover the asset in the content browser, and note that NativeClass points to a blueprint class