Add facilities for signal throttling and debouncing

[seanharmer]

As is commonly used in the js world or for e.g. https://github.com/KDAB/KDToolBox/tree/master/qt/KDSignalThrottler

Not sure which type of syntax would be most useful.

Maybe:

mySignal.debounce(100).connect(&MyClass::doSomething, myObj);

?