Introduce an Admin::EventScheduleController

- move SchedulesController#update action
- split it into an #create/#update and #destroy action and use these actions in the JS code

app/views/admin/schedule/_event.html.haml

@@ -7,7 +7,8 @@
 .schedule-event{ style: "height: #{height}px;  background-color: #{color}; color: #{contrast_color(color)}", |
                  id: "event-#{event.guid}", |
                  guid: event.guid, |
-                 length: cells_length }
+                 length: cells_length, |
+                 event_schedule_id: event_schedule_id }
   .schedule-event-text{ style: "-webkit-line-clamp: #{lines}; height: #{lines * 23}px;"}
     %span.schedule-event-delete-button{ onclick: "Schedule.remove(\'event-#{event.guid}\');" } X
     = event.title