Update Playground
Add an initial implementation of RoutedViewHost
Throw if we don't have a bundle

We have to do this or else we won’t create a new AppState
Don't schedule setting AppState

Scheduling this makes setting things up in your app’s OnCreate way
harder
NavigateCommandFor should create the VM if it's not reg'd
Ensure initial state of NavigateBack is correct
Rig Playground-XamForms to be a routing demo
Set the title correctly on pages
Make Android scheduler optimistic

This brings the scheduler in-line with the iOS scheduler (and also
solves some OnCreate ordering issues)
Stuff and things
Allow the Router to just be a property

Also, handle common mistakes like not registering views properly. We
still have to look up a Screen from the Locator though which kinds of
defeats the purpose of the router, because if you don’t present a view
immediately on construction, NavigationPage crashes
Merge pull request #724 from reactiveui/xamforms-routing

Xamarin Forms Routing