title: Preserve all classes in the shared project in release build
body: <p>I'm developing cross platform app using Xamarin.Forms, and I had some pain with the linker to build the release version. I use MVVM pattern, dependency injection for some services, value converters, behaviors, markup extensions... I've had to use the <code>[Preserve(AllMembers = true)]</code> attribute on many classes so that the linker wouldn't remove them.</p>
  
  <p>Is it any way to preserve all shared project classes and members without using <code>Preserve</code> attribute in all <em>"not used"</em> files?</p>