Adding <iface>.<router>.<domain> and <router>.<domain> A and AAAA rrs

The idea of this modification is to provide shorter domain names for
routers. Reverse entries are not modified as they already exist and
are associated to longer names.

For <router>.<domain>, at most one A and one AAAA are selected.
More intelligent selection could be interesting.
Merge branch 'master' of https://github.com/fingon/hnet-core
[DEBUG] Sometimes, lap's address is nil. This must be checked.
mdns zones' root is also forwarded so that anyone can resolve <iface>.<router>.<dom>
Merge pull request #3 from Oryon/master

Improve user-friendlyness by answering shorter dns requests