dnsdist: Split in two packages `dnsdist` and `dnsdist-full`

dnsdist: Split in two packages `dnsdist` and `dnsdist-full`

`dnsdist-full` has all optional features enabled, but is a big package
in term of both flash and memory footprint.
`dnsdist` only keeps the features that make the most sense
on embeded devices, but can also be customised to match the
user's needs, up to the point where it matches `dnsdist-full`.

Signed-off-by: Remi Gacogne <remi.gacogne@powerdns.com>