[AltStore] Revises AppViewController UI

- Fades in navigation bar as user scrolls down
- Displays version number, version date, and app size

AltStore/Components/NavigationBar.swift

@@ -31,4 +31,16 @@ class NavigationBar: UINavigationBar
         self.barTintColor = .white
         self.shadowImage = UIImage()
     }
+    
+    override func layoutSubviews()
+    {
+        super.layoutSubviews()
+        
+        // We can't easily shift just the back button up, so we shift the entire content view slightly.
+        for contentView in self.subviews
+        {
+            guard NSStringFromClass(type(of: contentView)).contains("ContentView") else { continue }
+            contentView.center.y -= 2
+        }
+    }
 }