Fetch source data: list Danbooru artist tag; elim duplicated code.

* In the `Fetch source data` box, list the Danbooru artist tag(s) that
  were found beside the artist name.

* Unify `Fetch source data` code that was duplicated between the
  uploads page and the post show page.

app/views/posts/partials/show/_edit.html.erb

@@ -4,7 +4,7 @@
   </div>
 <% end %>
 
-<%= render "sources/info_for_post" %>
+<%= render "sources/info" %>
 
 <%= form_for(post, :html => {:class => "simple_form", :id => "form"}) do |f| %>
   <%= hidden_field_tag :tags_query, params[:tags] %>