[development] image node type

[Moshe Weitzman]

> * My profile picture, handled as "just another file" rather than a special
>   case.

user picture is not a special case. user.module uses the file API exactly as 
it was designed. upload and image modules use file API to achieve their own 
goals.

one way to frame this discussion is to list additional services which ought 
to be provided by file API.

-moshe