Fixed DropShadow issue

Fixed an issue with the DropShadowEffect in the NavigatorWindowStyle of
AvalonDock.

src/Libraries/AvalonDock/AvalonDock/Resources/NavigatorWindowStyle.xaml

@@ -155,10 +155,17 @@
         <Setter Property="Template">
             <Setter.Value>
                 <ControlTemplate TargetType="{x:Type ad:NavigatorWindow}">
-                    <Border Width="574" Height="437" Background="{StaticResource NavigatorWindowBackground}" BorderBrush="{StaticResource NavigatorWindowBorderBrush}" BorderThickness="1" CornerRadius="3">
+                	<Border Background="Transparent">
                 		<Border.Effect>
-                            <DropShadowEffect BlurRadius="15"/>
+                            <DropShadowEffect BlurRadius="5" ShadowDepth="0"/>
                         </Border.Effect>
+	                    <Border Width="574"
+	                            Height="437"
+	                            Background="{StaticResource NavigatorWindowBackground}"
+	                            BorderBrush="{StaticResource NavigatorWindowBorderBrush}"
+	                            BorderThickness="1"
+	                            SnapsToDevicePixels="True"
+	                            CornerRadius="2">
 	                        <Grid>
 	                                <Grid.RowDefinitions>
 	                                    <RowDefinition Height="54"/>
@@ -224,6 +231,7 @@
 	                                </Border>
 	                            </Grid>
 	                	</Border>
+                	</Border>
                 </ControlTemplate>
                 
             </Setter.Value>