Do not use JS to initialize the schedule

- Only use JS for the drag&drop functionality and to the set/alter the time and rooms of the EventSchedule object.

- Introduce has_many :events, through: :event_schedules association to get unscheduled event easily

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

@@ -0,0 +1,13 @@
+- cells_length = event.event_type.length / EventType::LENGTH_STEP
+/ this height fits the room cells
+- height = (cells_length * 58) - 23
+/ subtracting the padding before calculate the number of lines
+- lines = (height - 7) / 23
+- color = event.track.try(:color).present? ? event.track.try(:color) : 'FFFFFF'
+.schedule-event{ style: "height: #{height}px;  background-color: #{color}; color: #{contrast_color(color)}", |
+                 id: "event-#{event.guid}", |
+                 guid: event.guid, |
+                 length: cells_length }
+  .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