Allow for SlidesContainer in edetail-lib@v1.0.1

@incuna/js I'm merging this and releasing straight away so we can get this into edetail-project
Only collections have `next` and `prev` and they return a model, so there should be a public manner to say "go to the next slide" which deals with getting the right model and selecting it. Are the refactoring changes you are mentioning going to move `nextSlide` and `prevSlide` off the view and onto the model/collection?