Fix issue with widget positions

Widget position are in a somewhat usable state now.

--HG--
branch : dev

src/Orchard.Web/Modules/Orchard.Widgets/Controllers/AdminController.cs

@@ -111,6 +111,9 @@ namespace Orchard.Widgets.Controllers {
                 if (widgetPart == null)
                     return HttpNotFound();
 
+                int widgetPosition = _widgetsService.GetWidgets(layerId).Count() + 1;
+                widgetPart.Position = widgetPosition.ToString();
+
                 widgetPart.LayerPart = _widgetsService.GetLayer(layerId);
                 dynamic model = Services.ContentManager.BuildEditor(widgetPart);
                 return View(model);

src/Orchard.Web/Modules/Orchard.Widgets/Models/WidgetPart.cs

@@ -28,7 +28,7 @@ namespace Orchard.Widgets.Models {
         /// <summary>
         /// The widget's position within the zone.
         /// </summary>
-        [HiddenInput(DisplayValue = false)]
+        [Required]
         public string Position
         {
             get { return Record.Position; }

src/Orchard.Web/Modules/Orchard.Widgets/Services/WidgetsService.cs

@@ -172,7 +172,7 @@ namespace Orchard.Widgets.Services {
 
         private static void SwitchWidgetPositions(WidgetPart sourceWidget, WidgetPart targetWidget) {
             string tempPosition = sourceWidget.Record.Position;
-            sourceWidget.Record.Position = targetWidget.ToString();
+            sourceWidget.Record.Position = targetWidget.Record.Position;
             targetWidget.Record.Position = tempPosition;
         }
     }