Remaining patches

These are all of my remaining patches that I hadn't submitted yet.

1. creation of a Node object similar to the MogileFS::FID object.
2. addition of a filepaths_remove_directory command.
3. add path_to_key support to cmd_updateclass.

I would have sent them individually, but 2 is dependent on 1 and 3 would have included all the history from 1 in the pull request