File attachments attributes

As a business user I would like to attach downloadable contents to SEO objects. E.g. product manuals (PDF), 3D swf views, T&C's downloadable PDF (on content page) etc.

TD:
1. New attribute type "Media"
2. Modifications to facilitate upload (some Image uploading code can be reused)
3. Modifications to facilitate import (some image import code can be reused)
4. MediaFilter to serve downloadable content (similar to ImageFilter), must be added to all storefront modules