Back navigation and shell improvements.

Wino.Core.Domain/Interfaces/IStatePersistenceService.cs

@@ -28,11 +28,6 @@ public interface IStatePersistanceService : INotifyPropertyChanged
     /// </summary>
     bool IsReaderNarrowed { get; set; }
 
-    /// <summary>
-    /// Should display back button on the shell title bar.
-    /// </summary>
-    bool IsBackButtonVisible { get; }
-
     /// <summary>
     /// Current application mode (Mail or Calendar).
     /// Not persisted to configuration, only kept in memory.
@@ -44,11 +39,6 @@ public interface IStatePersistanceService : INotifyPropertyChanged
     /// </summary>
     bool IsEventDetailsVisible { get; set; }
 
-    /// <summary>
-    /// Whether the current application mode has an active backstack that can be navigated.
-    /// </summary>
-    bool HasCurrentModeBackStack { get; set; }
-
     /// <summary>
     /// Setting: Opened pane length for the navigation view.
     /// </summary>

Wino.Core.Domain/Interfaces/IWinoNavigationService.cs

@@ -13,5 +13,6 @@ public interface INavigationService
 
     Type GetPageType(WinoPage winoPage);
     bool ChangeApplicationMode(WinoApplicationMode mode);
+    bool CanGoBack();
     void GoBack(NavigationTransitionEffect slideEffect = NavigationTransitionEffect.FromRight);
 }