Merge remote-tracking branch 'origin/netcore/netcore' into netcore/task/6973-migrating-authenticationcontroller

# Conflicts:
#	src/Umbraco.Infrastructure/PropertyEditors/PropertyEditorsComposer.cs

src/Umbraco.Web.UI.NetCore/Program.cs

@@ -21,10 +21,6 @@ namespace Umbraco.Web.UI.NetCore
                     x.ClearProviders();
                 })
                 .ConfigureWebHostDefaults(webBuilder => { webBuilder.UseStartup<Startup>(); })
-                // TODO: MSDI - this should probably be on one day, more so when we can reduce the number
-                // of times we build a ServiceProvider from services collection
-                // right now it's just painful.
-                .UseDefaultServiceProvider(options => options.ValidateOnBuild = false)
                 .UseUmbraco();
     }
 }