support chef-server 12

[arosenhagen]

I know v12 is still an RC but I think knife-server needs some adjustments to support it (additional/optional logic to install opscode-manage, opscode-analytics, opscode-reporting etc.)

[hh]

So many new options and artifacts for supporting chef-server 12. I don't think it's going to be a quick and easy one on it. Maybe it can be broken down into starting with just the main server itself.