mod reports: enable reporting for members, add dmail reporting.

* Add ability to report dmails.
* Enable reports for comments, forum posts, and dmails.
* Allow Members to send reports.
* Don't allow users to report the same thing twice.

config/locales/en.yml

@@ -37,6 +37,8 @@ en:
         url: ""
       forum_post_vote:
         creator_id: "Your vote"
+      moderation_report:
+        creator: "You"
       post:
         approver: "You"
         approver_id: "You"