do not send whole state on action

src/network.ml

@@ -3,3 +3,9 @@ let marshal o = Marshal.to_string o [] |> Format.sprintf "%S"
 let unmarshal o =
   let s = Scanf.sscanf o "%S" (fun s -> s) in
   Marshal.from_string s 0
+
+type server_message =
+  | Full_state of State.t
+  | Update_result of (State.action', string) result
+
+type client_message = Action_msg of State.action