chore(style): minor modified DataGrid.Small style

Author: NaBian

src/Net_40/HandyControl_Net_40/Themes/Theme.xaml

@@ -2715,7 +2715,7 @@
 		<Setter Property="Background" Value="White" />
 		<Setter Property="BorderBrush" Value="{DynamicResource BorderBrush}" />
 		<Setter Property="BorderThickness" Value="1" />
-		<Setter Property="HorizontalAlignment" Value="Center" />
+		<Setter Property="HorizontalAlignment" Value="Stretch" />
 		<Setter Property="VerticalAlignment" Value="Center" />
 		<Setter Property="VerticalContentAlignment" Value="Center" />
 		<Setter Property="Padding" Value="6,0,0,0" />
@@ -11715,7 +11715,7 @@
 		<Setter Property="BorderBrush" Value="Transparent" />
 		<Setter Property="BorderThickness" Value="0" />
 		<Setter Property="VerticalContentAlignment" Value="Center" />
-		<Setter Property="HorizontalContentAlignment" Value="Left" />
+		<Setter Property="HorizontalContentAlignment" Value="Stretch" />
 		<Setter Property="Padding" Value="{StaticResource DefaultControlPadding}" />
 		<Setter Property="hc:BorderElement.CornerRadius" Value="{StaticResource DefaultCornerRadius}" />
 		<Setter Property="Template">

src/Shared/HandyControl_Shared/Themes/Styles/Base/CheckBoxBaseStyle.xaml

@@ -19,7 +19,7 @@
         <Setter Property="Background" Value="White"/>
         <Setter Property="BorderBrush" Value="{DynamicResource BorderBrush}"/>
         <Setter Property="BorderThickness" Value="1"/>
-        <Setter Property="HorizontalAlignment" Value="Center"/>
+        <Setter Property="HorizontalAlignment" Value="Stretch"/>
         <Setter Property="VerticalAlignment" Value="Center"/>
         <Setter Property="VerticalContentAlignment" Value="Center"/>
         <Setter Property="Padding" Value="6,0,0,0"/>

src/Shared/HandyControl_Shared/Themes/Styles/Base/DataGridBaseStyle.xaml

@@ -34,7 +34,7 @@
         <Setter Property="BorderBrush" Value="Transparent"/>
         <Setter Property="BorderThickness" Value="0"/>
         <Setter Property="VerticalContentAlignment" Value="Center"/>
-        <Setter Property="HorizontalContentAlignment" Value="Left"/>
+        <Setter Property="HorizontalContentAlignment" Value="Stretch"/>
         <Setter Property="Padding" Value="{StaticResource DefaultControlPadding}"/>
         <Setter Property="hc:BorderElement.CornerRadius" Value="{StaticResource DefaultCornerRadius}"/>
         <Setter Property="Template">

src/Shared/HandyControl_Shared/Themes/Theme.xaml

@@ -2715,7 +2715,7 @@
 		<Setter Property="Background" Value="White" />
 		<Setter Property="BorderBrush" Value="{DynamicResource BorderBrush}" />
 		<Setter Property="BorderThickness" Value="1" />
-		<Setter Property="HorizontalAlignment" Value="Center" />
+		<Setter Property="HorizontalAlignment" Value="Stretch" />
 		<Setter Property="VerticalAlignment" Value="Center" />
 		<Setter Property="VerticalContentAlignment" Value="Center" />
 		<Setter Property="Padding" Value="6,0,0,0" />
@@ -11848,7 +11848,7 @@
 		<Setter Property="BorderBrush" Value="Transparent" />
 		<Setter Property="BorderThickness" Value="0" />
 		<Setter Property="VerticalContentAlignment" Value="Center" />
-		<Setter Property="HorizontalContentAlignment" Value="Left" />
+		<Setter Property="HorizontalContentAlignment" Value="Stretch" />
 		<Setter Property="Padding" Value="{StaticResource DefaultControlPadding}" />
 		<Setter Property="hc:BorderElement.CornerRadius" Value="{StaticResource DefaultCornerRadius}" />
 		<Setter Property="Template">