Split screen editing step demo

Usage instructions:

1. Check out this PR or branch
2. Start the server as per normal: ``node webodf/httpserver.js``
3. Point a browser towards http://127.0.0.1:8124/webodf/programs/editor/src-splitscreen.html
4. Log in on both clients (no user validation is performed)

# TODO
* [x] Add support for OT
* [x] Pause/play support to interrupt flow between clients
* [x] Quicker login?
* [ ] Randomise cursor colours to make it easier to see which user is which
* [ ] Let Bella loose in these!

# Pics
![screenshot from 2014-06-17 18 12 07](https://cloud.githubusercontent.com/assets/1052079/3297694/2b1369a8-f5f7-11e3-8be1-98c4d09247f5.png)

I've re-read the code a few times and can't see how the priority is at all defined by the order here. Can you please provide a concrete example?