Update the main doc page to a two-column format, and add a new section

Update the main doc page to a two-column format, and add a new section
called "Using the Apache HTTP Server" for task-oriented docs.  Also,
remove some of the "other notes" links that are more or less obsolete.
They are still available on a sub-page.

This is a little fancier than the old one, which I know will annoy
some people.  Oh well.

The design and HTML coding comes mostly from Carlos, but I messed it
up and changed stuff.  Blame Joshua for any errors.

Submitted by: Carlos Ramirez <cramirez@gte.net>, Joshua Slive

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@86787 13f79535-47bb-0310-9956-ffa450edef68