Document data file testing

[bwachter]

Many roles write configuration files. Do a proof of concept how to structure roles so that data files can be deployed to arbitrary directories for testing without having to execute the complete roles. We might have something similar already in some of the DNS/DHCP roles.

We also should be able to see if data files change between role updates - maybe creating an action that will commit the created data files to a test data branch in versioned subdirectories we can diff would be an option here.