Example code for loading XAML into a page and showing it for Xamarin.Forms

Used to answer this StackOverflow question: https://stackoverflow.com/questions/48769022/xamarin-forms-load-xaml-view-at-run-time/48769578#48769578

Also some more background info in this blog post: https://blog.verslu.is/xamarin/xamarin-forms-xamarin/loading-page-anything-xaml-string-xamarin-forms/