Add new freight module in a temporary namespace for testing

This is in the 'freight2' namespace so we don't break the freight module running on server09.

This module is intended to run on the web node (server2) and configures:

* freight package
* a freight user
* an SSH key to access the freight homedir
* a restrictive wrapper which only allows rsync to ~/rsync_cache
* the wrapper also performs the freight-add / freight-cache actions on incoming debs

The 'freight::client' class goes on the uploader (server09, eventually) and simply deploys the private part of the SSH key so it can push to freight@server. That key should probably go into ~jenkins later, but for testing it's in ~root

We need to test this by applying it to server2, adding the freight::client to server09, and then trying to push debs to server2. There's more work to do on how to process the incoming debs into the right pools, but that can be tested once this transport is working properly.