Allow to delete contests

config/locales/en.yml

@@ -202,6 +202,11 @@ en:
       title: Welcome %{username}!
       manage_contests: Manage my contests
       new_contest: Create a new contest
+    modals:
+      destroy:
+        button: Delete contest
+        text: You are about to delete the contest %{contest} and all its related data (participants, puzzles, ...). This action is non reversible, are you sure to want to proceed?
+        title: Deletion of contest %{contest}
     nav:
       categories: Participant categories
       categories_description: Once you add categories, you will be able to assign them to participants on their profiles, and a filter for categories will be available on the public scoreboard