download ISO directly istead of a zip file

[taukakao]

It seems like ISOs are already compressed, since the zip is not smaller than the ISO itself.

Thus, it would make sense to make the ISO downloadable directly and display the hash some other way on the same page.

[kbdharun]

The CDN (I think Hermes) would need to be updated to extract and upload the ISO and checksums separately to support this.