IM version 3 notes

* user's "sign up" for an id with a password
* user's sign-in using their id and password

Registration notes:

* All users are kept in the "users" namespace
* All "active" users are kept in the server namespace

There are four "Session" namespaces for each user:
* common
  used by all for new account registration.  This prevents two
  users from signing up for the same id at the same time

* The "browser cookie" session.
  used for all requests except registration and retrieving messages.

* The POST."browser cookie" session.
  used for retrieving messages.  This is a different session to prevent
  the request "blocked" on the message queue from preventing other
  requests from being satisfied.

* The msgsPOST."browser cookie" namespace.  This is used to store
  old messages.  Keeping them in a separate namespace allows us to
  "clear" all messages at once.

admin.html
  protected administrative management, such as deleting accounts, signing
  off users, etc.

bottom.html
  Message receiving frame

chat.html
  The main frameset/sign-in screen

logout.html
  The logout screen; sets the user to "logged-out" status

prefs.html
  Sets preferences

process.html
  message sending. Always returns "204 no content"

register.html
  User registrations

right.html
  The "right" frame, listing active users

stats.html
  A place holder for setting preferences.

top.html
  The "send message" entry box.

info.html
  Alternate interface designed for TCL client

notify.java
  Applet to do sound notifications when messages arrive.  The
  "notify.class" file should go in the "data" directory.
