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.cpp

@@ -0,0 +1,19 @@
+#include "U2F_CMD.hpp"
+#include "u2f.hpp"
+#include "U2F_Msg_CMD.hpp"
+#include "U2F_Init_CMD.hpp"
+
+using namespace std;
+
+shared_ptr<U2F_CMD> U2F_CMD::get(const shared_ptr<U2FMessage> uMsg)
+{
+	switch (uMsg->cmd)
+	{
+		case U2FHID_MSG:
+			return U2F_Msg_CMD::generate(uMsg);
+		case U2FHID_INIT:
+			return make_shared<U2F_Init_CMD>(uMsg);
+		default:
+			return {};
+	}
+}