Patch to support a more generalized search result than from_server_role

Hi,

I had the requirement to set different DNS resolvers in different Chef environments, so I added a new recipe to allow a generalized search to be used. This allows some cool things - the example in the updated README will serve.

Also, I didn't make a change to it, but the ipaddress:* filter in the default attribute is probably the kind of safety feature that should be added to from_server_role.