[monit] Documentation

[Sébastien Debrard]

Hi all !

I already know it's difficult to keep the documentation consistent and
complete. But good documentation will reduce the amount of questions
that are asked to the developers and provide them with more time code
in peace.

In the "svn documentation", the list of reserved keywords used by
monit should be completed with the lastest patch (radius patch -
keywords: radius, secret) and specific keywords used with SIP protocol
(keywords: target, maxforward).

Thanks to Martin for making time for this project.