Add logic for import of combination from xls files

StructureHelperCommon/Models/Forces/Logics/IGetTuplesFromFileLogic.cs

@@ -0,0 +1,12 @@
+using StructureHelperCommon.Infrastructures.Interfaces;
+using System.Collections.Generic;
+
+namespace StructureHelperCommon.Models.Forces
+{
+    public interface IGetTuplesFromFileLogic : ILogic
+    {
+        IColumnedFileProperty ForceFileProperty { get; set; }
+
+        List<IForceTuple> GetTuples();
+    }
+}