Change to the GFI import and the attachment downloads

- GFI import issue fixed with attribute ID 1 not existing causing the
import to fail for several attributes

- GFI import change: registry keys with binary value are now artifacts
dropped instead of persistance mechanism

- GFI import change: files with size of 0 will be omitted

- file attachment download change: moved away from the deprecated media
view in favour of cakeresponse->file()