Added explanation about discussions on open changesets

Closes #1705

app/views/browse/changeset.html.erb

@@ -72,6 +72,10 @@
         <input type="submit" name="comment" value="<%= t('javascripts.changesets.show.comment') %>" data-changeset-id="<%= @changeset.id %>" data-method="POST" data-url="<%= changeset_comment_url(@changeset) %>" disabled="1"/>
       </div>
     </form>
+  <% else %>
+    <div class="notice hide_unless_logged_in">
+    <%= t('browse.changeset.still_open') %>
+    </div>
   <% end %>
 
   <% unless @ways.empty? %>

config/locales/en.yml

@@ -131,6 +131,7 @@ en:
         title_comment: "Changeset %{id} - %{comment}"
       join_discussion: "Log in to join the discussion"
       discussion: Discussion
+      still_open: "Changeset still open - discussion will open once the changeset is closed."
     node:
       title: "Node: %{name}"
       history_title: "Node History: %{name}"