[enh] improved comment moderation email

templates/comments/comment_notification_email.txt

 {%load bt%}
-A comment has been posted on {{ content_object }}.
+A comment has been posted on {{ content_object }} by {{ comment.user }}.
 The comment reads as follows:
-{{ comment }}
+{{ comment.comment }}
 
 Approve: {%root_url%}/comments/approve/{{ comment.id }}/
 Delete: {%root_url%}/comments/delete/{{ comment.id }}/