Extend the jails chapter with the new section called "Application of
Jails". This section is going to provide a few examples how can be
jails used in production. Also bring in the first example, or howto,
called "Service Jails" which is basically based on a document
originally written by simon@ and an updated article by Ken Tom.

I think this section is in a pretty good shape, but any additional
grammar or logic updates are welcome!

Reviewed by: simon (I think only a bit),

		Jeremie Le Hen <jeremie(at)le-hen(dot)org>

Approved by: keramida (mentor), trhodes (mentor)