Fixed slider animate issue on return load

Issue: When stage value has been set, user returns to page, setStage tries to set the stage with widths before they have been determined correctly. This happens for as long as the jquery animation lasts.

Fix: Initially, a delay was put in to determine that the jquery animation on returning to the page was the cause, it was. So animateSliderToIndex has been changed to moveSlideToIndex and can take a boolean value, telling it whether to animate or not. On initial page load, we do not want it to animate. We therefore send setStage a secondary value when it is called from within setupNarrative, this let's setStage know that we're returning to the page, and are not trying to set the stage from the narrative controls.

Contribution also from @cajones