Installation instructions vs binaries

It's kind of strange that if you start your PostgreSQL journey by reading
our instructions, you get nothing useful about installing PostgreSQL from
binary packages other than "go ask somebody else about it". Yet we have
pretty good step by step instructions on our *website* for it.

Attached patch adds a chapter to the docs about installing from binaries,
and refers those users to the website download instructions (and updates
the Windows instructions to include an actual link to the website).

It also adds mention of it in a few other places - -there are probably more
that could use some help with that in the future. But I've seen a lot of
people get confused by our documentation assuming everything is from source
when it comes to initdb and pg_ctl that I think it's worth specially
mentioning it there.

--
Magnus Hagander
Me: https://www.hagander.net/ <http://www.hagander.net/>
Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>