move model validation into pattern classes and link from recurring_todo model

app/models/recurring_todos/daily_repeat_pattern.rb

@@ -7,9 +7,19 @@ module RecurringTodos
     end
 
     def every_x_days
-      @recurring_todo.every_other1
+      get :every_other1
     end
 
+    def only_work_days?
+      get :only_work_days
+    end
+
+    def validate
+      super
+      errors[:base] << "Every other nth day may not be empty for this daily recurrence setting" if (!only_work_days?) && every_x_days.blank?
+    end
+
+
   end
   
 end