Coding standards for entity.inc

Sorry, but this is a duplicate of #1533096: Make includes directory, files starting with D-G pass Coder Review and must be closed. I realize that other issue deals with Drupal 8, but work must be completed in Drupal 8 first then backported to Drupal 7. Also, that other issue is part of a much larger META issue to bring core code up to standard. Finally, issues tend to live in the 7.x queue for a long time. If the 8.0.x issue does eventually get committed then someone might start trying to backport it to 7.x and there would be duplication of work between these two issues.

Please feel free to move your patch over to that issue. It will be helpful later after the other issue is committed to 8.0.x.