Add comments referring to puppet in every file installed

In order to distinguish files on the system managed by puppet from those
provided by the system or a package (which may or may not be edited on
the system and then persist), we should document that a particular file
is installed by Puppet.

This applies the comment #5 to the other files managed by this module
Merge pull request #6 from alphagov/comment-files-installed

Add comments referring to puppet in every file installed