Add a cross-compiling notification class/method and/or qml

It does not make sense in having to implement a notification code for each platform when building cross-platform code.

For example, for desktops I'd be using snorenotify but then for android I need to use the "qt notifier" example to call a java method and add complexity for the code and for the build process.

A simple example :

class QNotify {

//...

public :

static notify(QString title, QString message);

//optional
static notify(QString title, QString message, std::chrono::seconds timeout=0s, QString path_to_image="");
}

The idea is to keep it simple at first, with local title/message based notifications.