Support any signal/slot signature in all interface

[stijnvanbeek]

Support for signals/slots with none or multiple arguments throughout the interface:

class SignalTest
{
public:
	SignalTest()
	{
		noArgsSignal.connect(noArgsSlot);
		argsSignal.connect(argsSlot);
		noArgsSignal();
		argsSignal(1, 0.5);
	}

	Signal<> noArgsSignal;
	Signal<int, float> argsSignal;

	Slot<> noArgsSlot = { this, &SignalTest::method };
	void method()
	{
		Logger::info("method");
	}

	Slot<int, float> argsSlot = { this, &SignalTest::method2 };
	void method2(int i, float x)
	{
		Logger::info("method2: %i, %f", i, x);
	}
};