Improving entity manager and entity support for a simpler version, made some cleanup on the road to support serialization of world

Juliet/include/Core/Common/serialization.h

@@ -0,0 +1,13 @@
+#pragma once
+
+struct Arena;
+
+struct archive
+{
+    Arena* arena;
+    bool   loading;
+};
+
+void serialize(archive* ar, void* data, size_t size);
+
+#define serialize_elem(ar, val) serialize((ar), &(val), sizeof(val))