C++ Implementation GameInstance save, also some cleanup of unsued C++ classes

This literally took me days, as it turn out that the timing offset between C++ and BP Init of GameIstance caused it to not be added as a GlobalObject to SPUD correctly.

VIRTUOS_ExpansionPluginTests/Source/VRExpPluginExample/Public/CustomAdvancedFriendsGI.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#include "CoreMinimal.h"
+#include "AdvancedFriendsGameInstance.h"
+#include "CustomAdvancedFriendsGI.generated.h"
+
+/**
+ * Custom GameInstance that registers itself with SPUD for persistence.
+ */
+UCLASS()
+class VREXPPLUGINEXAMPLE_API UCustomAdvancedFriendsGI : public UAdvancedFriendsGameInstance
+{
+    GENERATED_BODY()
+
+public:
+    virtual void Init() override;
+};