FZ - Styling updates to GridZone and CanvasZone controls so they look more Fluent (#1778)

* Improved styling so it looks more Fluent and native to W10

* CanvasZone border is now using the active accent color

* Updated GridZone to a similiar Fluent styling as the CanvasZone. Added a mouseover state to the GridResizer.

src/modules/fancyzones/editor/FancyZonesEditor/App.xaml

@@ -12,6 +12,10 @@
                 <!-- Accent and AppTheme setting -->
                 <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Themes/Light.Blue.xaml" />
             </ResourceDictionary.MergedDictionaries>
+
+            <SolidColorBrush x:Key="CanvasZoneBackgroundBrush" Color="#BF333333"/>
+            <SolidColorBrush x:Key="GridZoneBackgroundBrush" Color="#FF1a1a1a"/>
+            
         </ResourceDictionary>
     </Application.Resources>
 </Application>