group and subgroup adding/editing, services added

TimetableDesigner.Core/TimetableSpanCollision.cs

@@ -0,0 +1,17 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace TimetableDesigner.Core
+{
+    internal enum TimetableSpanCollision
+    {
+        CheckedSlotBefore,
+        CheckedSlotAfter,
+        CheckedSlotIn,
+        CheckedSlotFromIn,
+        CheckedSlotToIn
+    }
+}