Signed-off-by: Dirk Klimpel <dirk@klimpel.org>

Attempts to clarify the sample config for databases, and add some stuff about
tcp keepalives to `postgres.md`.

fix broken link

As using non-C locale can cause issues on upgrading OS.

Added database owner authentication with `sudo` when `su` does not work

Converting some of the rst documentation to markdown.  Attempted to
preserve whitespace and line breaks to minimize cosmetic change.