Added editShift to the model.

SchedulerApp/src/main/java/com/example/schedulerapp/Model.java

@@ -133,6 +133,10 @@ public class Model {
         writer.println("removeShift/"+shiftID);
     }
 
+    void editShift(int shiftID, String day, int start, int end) {
+        writer.println("editShift/"+shiftID+"/"+day+"/"+start+"/"+end);
+    }
+
     void printAllShifts() {
         System.out.println(this.shifts);
     }