* Add support to upload a picture to forum posts and replies, in forums that
have the PermitPhotos setting enabled.
* New DB table: CommentPhoto holds the association between a photo and a
forum ID. Photos can be uploaded at preview time (before a CommentID is
available) and get associated to the CommentID on save.
* Cron endpoint /v1/comment-photos/remove-orphaned can clean up orphaned
photos without a CommentID older than 24 hours.
* Add "Photo Boards" as a default forum category for new boards.
