Added resumable loading, along with signal handling.

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

U2FMessage.hpp

@@ -1,14 +1,21 @@
 #pragma once
 #include <cstdint>
 #include <vector>
+#include <memory>
 
 struct U2FMessage
 {
-	uint32_t        cid;
-	uint8_t         cmd;
-	std::vector<uint8_t> data;
+	public:
+		uint32_t        cid;
+		uint8_t         cmd;
+		std::vector<uint8_t> data;
 
-	static U2FMessage read();
+	public:
+		U2FMessage() = default;
+		U2FMessage(const uint32_t nCID, const uint8_t nCMD);
+		static std::shared_ptr<U2FMessage> readNonBlock();
+		void write();
 	
-	void write();
+	protected:
+		static void error(const uint32_t tCID, const uint16_t tErr);
 };