VectorMap<String, String> ConfigurationType;

template <class T>
bool testAddVector(String keyname, const T& t)
{
	ConfigurationType.Add(keyname, t); // You have implicitly tried to convert a string "Value" into a bool "Value" (hence the "Value" error)
	return true;
}

ValueMap vmap;

void TestValueMap(Value key, Value val) // Just change the key's signature to String if you want to limit the key type...
{
	vmap.Add(key, val);
}

CONSOLE_APP_MAIN
{
		StdLogSetup(LOG_COUT|LOG_FILE);
		
		String s = "world";
		testAddVector("Hello", s);
		DUMP(ConfigurationType.ToString());
		
		// If possible, I suggest using a ValueMap.
		
		TestValueMap("Hello", "World");
		TestValueMap(1, "This is a test");
		TestValueMap("This is a test too!", 2);
		
		DUMP(vmap);
}