schedule/events: add Track column

We no longer have rows with Track name so let add column with this
information.

Had to rename 'Attachments' into 'Files' to make table fit in page.

Author: hrw

content/schedule/events.html

@@ -21,10 +21,11 @@ <h1><%= size %> Events</h1>
         <tr>
             <th>Event</th>
             <th>Speakers</th>
+            <th>Track</th>
             <th>Room</th>
             <th>Start</th>
             <th>End</th>
-            <th>Attachments</th>
+            <th>Files</th>
 	    <th>Videos</th>
         </tr>
     </thead>
@@ -34,6 +35,7 @@ <h1><%= size %> Events</h1>
         <tr>
             <td><%= l(e) %></td>
             <td><%= l e[:speakers].map(&$to_speaker) %></td>
+            <td><%= l track e[:track] %></td>
             <td><%= l room e[:room] %></td>
             <td><%= l day e[:day] %> <%= e[:start_time] %></td>
             <td><%= e[:end_time] %></td>