CrackWidthCalculator has been added

StructureHelperLogics/NdmCalculations/Cracking/ICrackWidthLogicInputData.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace StructureHelperLogics.NdmCalculations.Cracking
+{
+    public interface ICrackWidthLogicInputData
+    {
+        /// <summary>
+        /// strain of rebar, dimensionless
+        /// </summary>
+        double RebarStrain { get; set; }
+        /// <summary>
+        /// strain of concrete, dimensionless
+        /// </summary>
+        double ConcreteStrain { get; set; }
+        /// <summary>
+        /// Length between cracks in meters
+        /// </summary>
+        double Length { get; set; }
+    }
+}