DNSSEC in wheezy

[Daniel Pocock <daniel@pocock.com.au>]

For some (probably many) people, an upgrade from squeeze (or earlier) to
wheezy may be their first real experience of DNSSEC

I've tried to update the wiki page to help people who are completely new
to the subject.  However, I'm sure there are people who may be able to
provide more specific comments or links they found useful

In particular, I've extended the introduction
http://wiki.debian.org/DNSSEC#What_is_DNSSEC

and added a table comparing squeeze and wheezy support for those who
prefer such a two-dimensional summary.