Swing interop: app should not need to explicitly initialize the FX runtime

Currently, a swing application must call Application.launch, passing in a subclass of Application. This is cumbersome and error prone. In the most recent build, I have factored this out into a dummy class in SwingJavaFXChart as follows:

    //NOTE: this method of launching the JavaFX runtime is temporary and will
    // be superseded by a method on JFXPanel itself.
    public static class TmpFxLauncher extends Application {
        @Override public void start(Stage primaryStage) {
        }

        private static void launch() {
            Application.launch(null);
        }
    }

This can go away as soon as we settle on exactly how we want to launch FX from JFXPanel. Regardless of how we do it, a Swing / FX interop app should not need to refer to the Application class.

I recommend making initialization implicit when the first JFXPanel instance is constructed.