Improve selection of name to display in data browser

If the user is logged in then consider all their preferred
languages rather than just the UI language, and use the full
locale matching algorithm instead of just checking parents.

Fixes #2636

test/helpers/browse_helper_test.rb

@@ -151,4 +151,10 @@ class BrowseHelperTest < ActionView::TestCase
       create(:node_tag, :node => node, :k => key, :v => value)
     end
   end
+
+  private
+
+  def current_user
+    nil
+  end
 end