Events: implement creation of new contests

config/locales/en.yml

@@ -293,9 +293,11 @@ en:
     index:
       contest: contest
       contests: contests
+      manage_contests: Contests in this event
       message: New feature! Events offer to groupe multiple contests in one management space. This also offers, if activated, to have a single scoreboard link for all contests of an event.
       my_contests_outside_events: My contests not linked to any event
       new: Create a new event
+      new_contest: Add a contest to this event
       subtitle: My events
       title: Welcome %{username}!
     new: