Add label_news (singular) for languages where this can be distinguished (e.g. German)

[ci skip]

app/views/news/index.html.erb

@@ -40,7 +40,7 @@ See docs/COPYRIGHT.rdoc for more details.
             aria: {label: t(:label_news_new)},
             title: t(:label_news_new)} do %>
         <%= op_icon('button--icon icon-add') %>
-        <span class="button--text"><%= t('activerecord.models.news') %></span>
+        <span class="button--text"><%= t(:label_news) %></span>
       <% end %>
     </li>
   <% end %>

config/locales/en.yml

@@ -1493,6 +1493,7 @@ en:
   label_new: "New"
   label_new_features: "New features"
   label_new_statuses_allowed: "New statuses allowed"
+  label_news: "News"
   label_news_added: "News added"
   label_news_comment_added: "Comment added to a news"
   label_news_latest: "Latest news"