Added resumable loading, along with signal handling.

This version can store state after receiving SIGINT.
This is achieved by polling FIFO read state;

U2F_CMD.hpp

@@ -1,4 +1,6 @@
 #pragma once
+#include <memory>
+#include "U2FMessage.hpp"
 
 struct U2F_CMD
 {
@@ -6,5 +8,7 @@ struct U2F_CMD
 		U2F_CMD() = default;
 
 	public:
-		~U2F_CMD() = default;
+		virtual ~U2F_CMD() = default;
+		static std::shared_ptr<U2F_CMD> get(const std::shared_ptr<U2FMessage> uMsg);
+		virtual void respond(const uint32_t channelID) const = 0;
 }; //For polymorphic type casting