Allow man page generator to handle somewhat older (or newer!) versions of Puppet

It's possible that we'll need to generate man pages for versions of Puppet where
some of the subcommands in the categories either don't exist yet or were
removed. This commit checks the category lists and bounces out any absent
subcommands so they won't appear in the index.
Allow man pages to appear for 3.3.1+ and 2.7.23+

Previously we were only allowing for 3.4+, but this lets us publish man pages
now for the most recent versions in both the 2.7.x and 3.x series.
Generate man pages for 3.3.1 and 2.7.23
Update all links to man pages to point to appropriate version