Include more news on the front page

This is mostly to balance the left and right columns.
Fix downloading of ec2-amis.nix
Hide scary research papers
Use curl --fail
Checkpoint
Update Disnix styling
Checkpoint
Checkpoint
Include news.css in nixos-site.css
Nix blurb
Short NixOps blurb
Tweak
Update GRUB screenshot
Add NixOps screenshot
Add link to NixOps