Clean up the notes to the logformat section of the mod_log config docs.

Clean up the notes to the logformat section of the mod_log config docs.
These have been growing using the "here's something else we should
say" technique, without any serious thought for readability.

In particular:

- Remove the "..." in all the format strings, since almost nobody
uses this and it can be confusing.  It is still documented, just
not included in the definitions.

- Create three sections: modifiers, examples, and a "notes" section
for stuff that doesn't go any place else.

- Remove the discussion of %v being the canonical name.  I think
that it is quite clear since the addition of %V what the difference
is.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@178530 13f79535-47bb-0310-9956-ffa450edef68