Split dns-server into 2 different roles. [1/2]

This pull request set splits dns-server into 2 smaller roles:

* dns-server, which does the initial setup of bind, and
* dns-database, which is reasposible for ongoing maintenance of the
bind9 zone for the admin network of the cluster.

This also adds some infrastructure in the Crowbar barclamp to
facilitate poking the dns-database role whenever a node is created or
destroyed.


 .../app/models/barclamp_crowbar/jig.rb             |  1 -
 crowbar_framework/app/models/node.rb               |  9 ++++
 crowbar_framework/app/models/node_role.rb          | 49 +++++++++++++++-------
 crowbar_framework/app/models/role.rb               |  1 +
 4 files changed, 44 insertions(+), 16 deletions(-)

Crowbar-Pull-ID: 763d805705b2c4a304d3ae9606be913bd4cca504

Crowbar-Release: development