Choosing a song and only uploading it on node save doesn't auto-set 'private' and 'sell' checkboxes

Fixed with this commit: http://drupal.org/cvs?commit=418740

It meant fixing how the 'sell' checkboxes work on the node edit form, by making sure the _ec_file_form_submit() function properly emulates theme_upload_form_current() and then getting the logic to work correctly, like follows:

* If a file has been uploaded and the "sell" checkbox is checked, we add it to the ec_file table.
* If a file has been selected but not uploaded yet, and the default file selling settings are set to "yes" then mark it as private and sell-able.
* Also handles cases where it's a file that's not being sold any more, or if it's been deleted.