unittest folder added

unittest/internal/UnittDefinitions.cpp

@@ -0,0 +1,7 @@
+#include <fsfw/unittest/internal/UnittDefinitions.h>
+
+ ReturnValue_t unitt::put_error(std::string errorId) {
+	sif::error << "Unit Tester error: Failed at test ID "
+			<< errorId << "\n" << std::flush;
+	return HasReturnvaluesIF::RETURN_FAILED;
+}