Measurements of units were added

Infrastructure/UI/Converters/IStringDoublePair.cs

@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace StructureHelper.Infrastructure.UI.Converters
+{
+    internal interface IStringDoublePair
+    {
+        double Digit { get; }
+        string Text { get; }
+    }
+}