Move CalendarDatePickerFormat into its own file

src/Avalonia.Controls/Calendar/CalendarDatePicker.cs

@@ -15,30 +15,6 @@ using Avalonia.Interactivity;
 
 namespace Avalonia.Controls
 {
-    /// <summary>
-    /// Specifies date formats for a
-    /// <see cref="T:Avalonia.Controls.CalendarDatePicker" />.
-    /// </summary>
-    public enum CalendarDatePickerFormat
-    {
-        /// <summary>
-        /// Specifies that the date should be displayed using unabbreviated days
-        /// of the week and month names.
-        /// </summary>
-        Long = 0,
-
-        /// <summary>
-        /// Specifies that the date should be displayed using abbreviated days
-        /// of the week and month names.
-        /// </summary>
-        Short = 1,
-
-        /// <summary>
-        /// Specifies that the date should be displayed using a custom format string.
-        /// </summary>
-        Custom = 2
-    }
-
     [TemplatePart(ElementButton,   typeof(Button))]
     [TemplatePart(ElementCalendar, typeof(Calendar))]
     [TemplatePart(ElementPopup,    typeof(Popup))]

src/Avalonia.Controls/Calendar/CalendarDatePickerDateValidationErrorEventArgs.cs

@@ -1,4 +1,9 @@
-using System;
+// (c) Copyright Microsoft Corporation.
+// This source is subject to the Microsoft Public License (Ms-PL).
+// Please see http://go.microsoft.com/fwlink/?LinkID=131993 for details.
+// All other rights reserved.
+
+using System;
 
 namespace Avalonia.Controls
 {

src/Avalonia.Controls/Calendar/CalendarDatePickerFormat.cs

@@ -0,0 +1,31 @@
+// (c) Copyright Microsoft Corporation.
+// This source is subject to the Microsoft Public License (Ms-PL).
+// Please see http://go.microsoft.com/fwlink/?LinkID=131993 for details.
+// All other rights reserved.
+
+namespace Avalonia.Controls
+{
+    /// <summary>
+    /// Specifies date formats for a
+    /// <see cref="T:Avalonia.Controls.CalendarDatePicker" />.
+    /// </summary>
+    public enum CalendarDatePickerFormat
+    {
+        /// <summary>
+        /// Specifies that the date should be displayed using unabbreviated days
+        /// of the week and month names.
+        /// </summary>
+        Long = 0,
+
+        /// <summary>
+        /// Specifies that the date should be displayed using abbreviated days
+        /// of the week and month names.
+        /// </summary>
+        Short = 1,
+
+        /// <summary>
+        /// Specifies that the date should be displayed using a custom format string.
+        /// </summary>
+        Custom = 2
+    }
+}