support for .NET framework 3.5

Still have bugs

Net35/HandyControl_Net35/Themes/Basic/Sizes.xaml

@@ -0,0 +1,8 @@
+<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+                    xmlns:system="clr-namespace:System;assembly=mscorlib">
+
+    <system:Double x:Key="DefaultControlHeight">30</system:Double>
+    <Thickness x:Key="DefaultControlPadding">12,6</Thickness>
+
+</ResourceDictionary>