Move GetTopViewController -> GetTopModalHostViewController to extension methods

Remove unnecessary methods from IMvxIosViewPresenter

MvvmCross/Platform/iOS/Views/Extensions.cs

@@ -176,5 +176,17 @@ namespace MvvmCross.iOS.Support.Views
 
 			return descendantViews;
 		}
+
+        public virtual UIViewController GetTopModalHostViewController(this UIWindow window)
+        {
+            var vc = window.RootViewController;
+            do {
+                if (vc.PresentedViewController != null)
+                    vc = vc.PresentedViewController;
+
+            } while (vc.PresentedViewController != null);
+
+            return vc;
+        }
     }
 }

MvvmCross/Platform/iOS/Views/Presenters/IMvxIosViewPresenter.cs

@@ -11,13 +11,6 @@ using UIKit;
 namespace MvvmCross.iOS.Views.Presenters
 {
     public interface IMvxIosViewPresenter : IMvxViewPresenter, IMvxCanCreateIosView
-    {
-        void ShowModalViewController(UIViewController viewController, bool animated);
-
-        void CloseModalViewController(UIViewController viewController);
-
-        void CloseModalViewControllers();
-
-        UIViewController GetTopViewController();
+    {    
     }
 }

MvvmCross/Platform/iOS/Views/Presenters/MvxIosViewPresenter.cs

@@ -532,18 +532,6 @@ namespace MvvmCross.iOS.Views.Presenters
             SplitViewController = null;
         }
 
-        public virtual UIViewController GetTopViewController()
-        {
-            var vc = UIApplication.SharedApplication.KeyWindow.RootViewController;
-            do {
-                if (vc.PresentedViewController != null)
-                    vc = vc.PresentedViewController;
-
-            } while (vc.PresentedViewController != null);
-
-            return vc;
-        }
-
         protected void RemoveWindowSubviews()
         {
             foreach (var v in _window.Subviews)