added remind tasks (3,4,6,9 months)

default/list_task_models/remind.3month.task

+title.gettext reminder message sent to subscribers every 3 months
+
+/INIT
+next([execution_date]+3m,EXEC)
+
+/EXEC
+@selection = select_subs (older([execution_date]))
+send_msg (@selection, remind)
+next([execution_date]+3m,EXEC)

default/list_task_models/remind.4month.task

+title.gettext reminder message sent to subscribers every 4 months
+
+/INIT
+next([execution_date]+4m,EXEC)
+
+/EXEC
+@selection = select_subs (older([execution_date]))
+send_msg (@selection, remind)
+next([execution_date]+4m,EXEC)

default/list_task_models/remind.6month.task

+title.gettext reminder message sent to subscribers every 6 months
+
+/INIT
+next([execution_date]+6m,EXEC)
+
+/EXEC
+@selection = select_subs (older([execution_date]))
+send_msg (@selection, remind)
+next([execution_date]+6m,EXEC)

default/list_task_models/remind.9month.task

+title.gettext reminder message sent to subscribers every 9 months
+
+/INIT
+next([execution_date]+9m,EXEC)
+
+/EXEC
+@selection = select_subs (older([execution_date]))
+send_msg (@selection, remind)
+next([execution_date]+9m,EXEC)