Ground work for Wino Calendar. (#475)

Wino Calendar abstractions.

Wino.Core.UWP/Converters/GridLengthConverter.cs

@@ -0,0 +1,27 @@
+using System;
+using Windows.UI.Xaml.Data;
+using Windows.UI.Xaml;
+
+namespace Wino.Converters
+{
+    public class GridLengthConverter : IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter, string language)
+        {
+            if (value is double doubleValue)
+            {
+                return new GridLength(doubleValue);
+            }
+            return new GridLength(1, GridUnitType.Auto);
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, string language)
+        {
+            if (value is GridLength gridLength)
+            {
+                return gridLength.Value;
+            }
+            return 0.0;
+        }
+    }
+}