* tmcd/ron: A new directory of client code, based on the freebsd
  client code, but scaled back to the bare minimum. Does only account
  and group file maintenance. I redid the account stuff so that only
  emulab accounts are operated on. Does not require a stub file, but
  instead keeps a couple of local dbm files recording what groups and
  accounts were added by Emulab. There is a ton of paranoia checking
  to make sure that local accounts are not touched.

  The update script that runs on the client node detaches so that the
  ssh from boss returns immediately. update can also be run from the
  node periodically and at boottime. The script is installed setuid
  root, but checks to make sure that *only* root or "emulabman" has
  invoked it.

* utils/sshremote: New file. For remote nodes, instead of using sshtb,
  use sshremote, which ssh's in as "emulabman", which needs to be a
  local non-root user, but with an authorized_keys file containing
  boss' public key.

* web interface changes: Allow user to specify his own public key in
  addition to the emulab key.

  Add option in showexp page to update accounts on nodes in the
  experiment. I was originally intending to do this from approveuser,
  but this was easier and faster. I will add an option to do it on the
  approveuser page later.

* libdb.pm: Add a TBIsNodeRemote() query to see if a node is in the
  local testbed or a pcRemote node. Currently, this test is hardwired
  to a check for class=pcRemote, but this will need to change to a
  node_types property at some point.

* node_update: Reorg so that there is a maximum number of children
  created. Previously, a child was forked for each node, but that
  could chew up too many processes, especially for remote nodes which
  might hang up. For the same reason, we need to "lock" the experiment
  so that it cannot be terminated while a node_update is in progress.
  Might be to relax that, but this was easy for now. Also add
  distinction between local and remote, since for remote we use
  sshremote insted of sshtb. Various cleanup stuff

* mkacct; When generating a new account, include user supplied pub key
  in the authorized keys file, in addition to the eumlab generated
  key. Both keys are stored in the DB in the users table. Anytime we
  update an account, get a fresh copy of the emulab pub key, in case
  user changes it.