Support subdirs for projects

I work for several clients and want to keep their projects namespaced in Boxen e.g. `projects::awesome client::amazingproject` in `modules/projects/manifests/client/amazingproject.pp`.

It's entirely possible to do this using underscores, but it doesn't feel as nice as having separate directories for each client.

Note that this may change the name of some servers where an underscore was used in the project name. I prefer this way, but I can alter the code to support having underscores too, either way.