handlers: Introduce HandlerVersion to return the verison string

handlers/handlerversion.cpp

@@ -0,0 +1,9 @@
+#include "handlerversion.h"
+#include "../version.h"
+Response HandlerVersion::handleRequest(const Request &r)
+{
+	Response response;
+	response.setContentType("text/plain");
+	response.setBody(get_version_string());
+	return response;
+}