Improve lister/loader tables presentation

Logos in the loader table were taking too much space, resulting in unfortunate line breaks in other columns. Let’s reduce their width to a minimum instead.

Also remove the secondary sidebar to get some extra space.

Finally, instead of repeating the word “loader” on every line (for example “Arch loader”, “Bazaar loader”, “RubyGems loader”), let’s just use the name directly.

Also fixes tables not being rebuilt when changing the generation script.