This adds a top-level document for the new `to` command, with a list (of links) of all the subcommands.
All the to-* subcommands keep their filename, but the content is updated to use the new subcommand syntax.
Since not all subcommands have documentation, some items in the list are just text without a link. Also filled the list for the undocumented from* commands in the same style.
Fixes#1709
