metadata and the data itself JSON encoded, we just send back the raw
data with the right Content-Type. This, combined with code in
Item_Model::as_restful_array() that swaps in /rest/data urls as
appropriate, means that the RESTful payload has consistent urls when
permissions are in play.
robust in the face of a missing data file (movies and albums lack
resize, albums lack full size, some albums don't have a thumb if they
have no contents, etc)
contents of the file, which enables REST viewers to see the actual
data which is useful when the files are privileged. Currently it
returns the contents of the file in JSON encoded form, which may not
be the best. Multipart/mime might be much better.
Fixes ticket #1224.
