support for .NET framework 3.5

Still have bugs

Net35/HandyControl_Net35/Themes/Styles/Image.xaml

@@ -0,0 +1,8 @@
+<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
+
+    <Style TargetType="Image">
+        <Setter Property="Stretch" Value="Uniform" />
+        <Setter Property="RenderOptions.BitmapScalingMode" Value="HighQuality" />
+    </Style>
+
+</ResourceDictionary>