split named.conf

* move options to a separate file
* move zone definition to a separate file
* this way changing things when it's necessary will be easier
add the current buildbot.net zone

* as it was given in http://trac.buildbot.net/ticket/3002
simplified zone definition
first important task
make buildbot.net zone a template

* move the file
* create a variable to describ hostmaster
* create variables to describe secondary NSes
* use the variables to create actual content
ip addresses of secondaries are actually required

* main reason: restrict zone transfers to secondaries only
* another option is to resolve them at the time of installation (which
  might be or not a good idea)
generate rndc.key if it's not present

* configure named to allow operations with this key
install configuration files

* introduce a variable that points to the target directory
* update tasks to use the variable
* create necessary directories
* copy necessary files
* install buildbot.net zone
* update configuration templates to use the variable
* install configuration files using the templates
* add handler to reload configuration upon change
* enable and start named service
move traditional root hinting and rfc related zones to a separate file

* this makes the main config file a bit more manageable
update named.conf.options
make buildbot.nte a master

* IP addresses of secondaries were not needed after all as a particular
  slave would be pulling the zone (which is configured in
  named.conf.zones