[Dev Tools NG] Icon overlay should be displayed for all rated files

E.g., package.html files are included into the rating, but no icon overlay is shown to indicate the rating

In the frame of this ticket it should be reconsidered which file types are included into the rating. Ultimately, the rating should be visualized for all file types that are not included into the whitelist of file extensions for which no rating is computed.

(from redmine: issue id 3195, created on 2017-11-28, closed on 2017-11-30)