title: Xamarin - How to update Mono.Android version to resolve dependencies?
body: <p>I'm trying to install a nuget package (Xamarin.Firebase.Firestore) which requires a newer version of Xamarin.GooglePlayServices.Basement (60.1142.0, I have 42.1021.1), which in turn requires me to update the xamarin.android.support packages. When I try to update those, I get this error 
  "Package Xamarin.Android.Support.Design 27.0.2 is not compatible with monoandroid80 (MonoAndroid,Version=v8.0). Package Xamarin.Android.Support.Design 27.0.2 supports: monoandroid81 (MonoAndroid,Version=v8.1)"</p>
  
  <p>I've tried changing my target android version to 8.1, I've also updated my SDK as well as the build tools. I'm running Visual Studio 15.6.1. As a last ditch effort, I tried deleting the Mono.Android V8.0 reference and then adding a new reference to V8.1, but whenever I do so, Visual studio just ends up adding the reference with the path pointing to V8.0, even though the reference I added was clearly pointing to V8.1. </p>
  
  <p>Anyone has a clue how to resolve this issue? </p>