Add more changes relating to authorative only servers

This change disables, the following parameters as they are not relevent in authorative only server and where causing high CPU usage

  * dnssec-validation
  * dnssec-lookaside

I have also changed the default value for dnssec-lookaside, this gives recursive operators a method of disabling dnssec-lookaside.  I have added an additional parameter for bindkeys_file instead of having one hard coded in server.conf.  the one you have in your config dose not exist on ubuntu 12.04 LTS however the default one (bind.keys) does.   I also changed the default of dnssec-validation to auto which i think makes more sense then yes.

Finally it looks like this pull request has some documentation and a few other small fixes missed from my last pull

John