- The component isn't ready immediately, so instatiate
once it is fully loaded and ready
- Edge case if the execution view step is already visible, then
start the show (because a previous call to onActivate() will
have missed it).
- Load QML on startup, compile async
- Create QML component when the page is reached.
- On leave, stop the slideshow (otherwise, e.g. timers will keep running)
This should move some of the delay from loading a large
slideshow forward as the engine is already initialized when
we reach the install / slideshow page.
