file_proxy. It also means we can stop munging file names in the var/resizes hierarchy.
In the process, rename "thumbnail" to "thumb" everywhere in honor of
Chad (well, ok because it's shorter)..
* Media_RSS_Controller::$LIMIT is now self::$page_size
* We use ORM_MPTT descendant_counts()
* If the page is out of bounds, put it on a boundary
* Move pub_date into the controller to simplify the mrss file
* Put all the view assignment in one block for easier reading
* Removed stray ; from the end of lines in the mrss file
Clean up ORM_MPTT a bit:
* fix spelling: decendent -> descendant
* Remove unnecessary order_by() clauses
* Set the default for $type to null (not "all").
