Import basic dirvish module

This is for starting to automate some backups. We have an internal redhat host, this will get `dirvish` but initially only told to back up it's own stuff. Then we can test adding more things to the `vaults` hash, and potentially adding custom pre_backup scripts for certain hosts via the `dirvish::client::pre_(template|script)` parameter.

This is mainly for review - I'll try to push my latest changes to my dirvish module's github repo and we can use it as a submodule when we're ready to commit.

@skottler care to review? I use this for my house backups, so it works reasonably well. The only downside is it the initial puppet run can take a _looooong_ time on a large backup set :).