use System.Runtime instead of mscorlib

src/Shared/HandyControl_Shared/Themes/Basic/Colors/Colors.xaml

@@ -1,6 +1,6 @@
 <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">
+                    xmlns:system="clr-namespace:System;assembly=System.Runtime">
 
     <Color x:Key="LightPrimaryColor">#f3fbff</Color>
     <Color x:Key="PrimaryColor">#326cf3</Color>

src/Shared/HandyControl_Shared/Themes/Basic/Colors/ColorsDark.xaml

@@ -1,6 +1,6 @@
 <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">
+                    xmlns:system="clr-namespace:System;assembly=System.Runtime">
 
     <Color x:Key="LightPrimaryColor">#044289</Color>
     <Color x:Key="PrimaryColor">#326cf3</Color>

src/Shared/HandyControl_Shared/Themes/Basic/Colors/ColorsViolet.xaml

@@ -1,6 +1,6 @@
 <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">
+                    xmlns:system="clr-namespace:System;assembly=System.Runtime">
 
     <Color x:Key="LightPrimaryColor">#fefbff</Color>
     <Color x:Key="PrimaryColor">#7b1fa2</Color>

src/Shared/HandyControl_Shared/Themes/Basic/Fonts.xaml

@@ -1,6 +1,6 @@
 <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">
+                    xmlns:system="clr-namespace:System;assembly=System.Runtime">
 
     <system:Double x:Key="LargeFontSize">24</system:Double>
     <system:Double x:Key="HeadFontSize">20</system:Double>

src/Shared/HandyControl_Shared/Themes/Basic/Sizes.xaml

@@ -1,6 +1,6 @@
 <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">
+                    xmlns:system="clr-namespace:System;assembly=System.Runtime">
 
     <system:Double x:Key="DefaultControlHeight">30</system:Double>
     <Thickness x:Key="DefaultControlPadding">10,6</Thickness>