Refactor project from Ghost.App to Ghost.Editor

Changed the project structure to reflect a shift from `Ghost.App` to `Ghost.Editor`, updating namespaces and class names throughout.

Changed the application class in `App.xaml` and `App.xaml.cs` from `GhostApplication` to `EditorApplication`.

Changed several service interfaces to reside under `Ghost.Editor.Services.Contracts`, including `IInspectorService`, `INotificationService`, and `IProgressService`.

Added `InspectorView` and `InspectorViewModel` classes to manage inspector functionality.

Added `NavigationTabView` and `NavigationTabPage` classes to facilitate navigation within the editor.

Enhanced `WorldNode` and `EntityNode` classes to support scene graph functionality, including serialization and entity management.

Updated the project file `Ghost.Editor.csproj` to reflect the new structure and removed old references.

Modified the solution file `GhostEngine.sln` to remove references to `Ghost.App` and include `Ghost.Editor`.

Updated unit tests to align with the new namespaces and project structure.

Ghost.Editor/SceneGraph/WorldNode.cs

@@ -167,7 +167,12 @@ public partial class WorldNode : SceneGraphNode, IEquatable<WorldNode>
 
 public partial class WorldNode : IInspectable
 {
-    public UIElement OnInspectorDraw()
+    public UIElement HeaderContent()
+    {
+        throw new NotImplementedException();
+    }
+
+    public UIElement InspectorContent()
     {
         throw new NotImplementedException();
     }