Adds chef generate repo support

Creates a chef-repo that is identical to the current state of
github's opscode/chef-repo repository.

Has options that match those of knife cookbook create, for
license, copyright holder, etc.

Includes --policy-only support, which puts the cookbook
directory into .gitignore and adds a different README
file.
I purposefully didn't change a word from the standing chef-repo, since I want the goal to be moving existing users over to the new standard. Rule one of organizing, meet people where they are.