Ground work for Wino Calendar. (#475)

Wino Calendar abstractions.

Wino.Calendar/Styles/DayHeaderControl.xaml

@@ -0,0 +1,23 @@
+<ResourceDictionary
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:controls="using:Wino.Calendar.Controls">
+
+    <!--  Left day header DayHeaderControl  -->
+    <Style TargetType="controls:DayHeaderControl">
+        <Setter Property="Template">
+            <Setter.Value>
+                <ControlTemplate TargetType="controls:DayHeaderControl">
+                    <Grid>
+                        <TextBlock
+                            x:Name="PART_DayHeaderTextBlock"
+                            HorizontalAlignment="Center"
+                            VerticalAlignment="Top"
+                            FontSize="12" />
+                    </Grid>
+                </ControlTemplate>
+            </Setter.Value>
+        </Setter>
+    </Style>
+
+</ResourceDictionary>