Make it possible to select favourites events

Make it possible for users to select events which they want to see in the public schedule and in the All events section of the public schedule.

app/views/schedules/_event.html.haml

@@ -4,11 +4,15 @@
       = image_tag speaker.gravatar_url, :class => "img-circle pull-right all-speaker-pic", |
                                         :alt => speaker.name, |
                                         :title => speaker.name |
-
     %p
       = canceled_replacement_event_label(event, event_schedule)
       = replacement_event_notice(event_schedule)
-
+    - if current_user
+      = link_to('#', onClick: 'starClicked();') do
+        %span#star-events{ class: "fa fa-lg #{ event.favourite_users.exists?(current_user.id) ? 'fa-star' : 'fa-star-o' }", |
+                           "aria-hidden" => "true", |
+                           "data-url" => conference_program_proposal_path(@conference.short_title, event.id), |
+                           "data-user" => current_user.id }
     %span.h3
       = event.title
       %br