Moves the uploading Attachments queue from the media workspace view to the uploader itself. This ensures that all attachments are added to the central attachmnet store.
Updates wp.Uploader to pass Attachment models to callbacks instead of Plupload file objects. Attachments in the process of uploading have a reference to the file object (which can be fetched by calling `attachment.get('file');`).
Also updates the customizer to be compatible with the API changes.
git-svn-id: https://develop.svn.wordpress.org/trunk@21814 602fd350-edb4-49c9-b593-d223f7449a82
1cc9c42bc4