Add user manifest

This commit adds a user manifest and pulls the username and public key in from Hiera. It limits the user to the rSSH shell in order such that the user can only use rsync, and nothing else. This is a security measure.
Add authorized keys
Adds relevant .gitkeep placeholders

This commit adds .gitkeep placeholders ensuring we don't lose folder structure.
Merge branch 'add-auth-ssh-key' into add-user-manifest
Merge branch 'add-user-manifest' into add-hiera