Split screen editing 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
* [x] Randomise cursor colours to make it easier to see which user is which
* [x] ~~Fix op priorities so it's per memberid~~ (not an existing problem. My understanding here was flawed)
* [x] ~~Let Bella loose in these!~~ (won't happen in this PR)

# Pics
![screenshot from 2014-06-17 18 12 07](https://cloud.githubusercontent.com/assets/1052079/3297694/2b1369a8-f5f7-11e3-8be1-98c4d09247f5.png)

In case there are meanwhile new ops on the server, this will result in a call of `logErrorAndRetry`, which will result in call of `completeSyncRequest(false)` which will call `updateHasSessionHostConnectionState(false)` which... seems wrong to me, because the connection is all fine, it is just that the other client was quicker with pushing their latests ops. So the call to `updateHasSessionHostConnectionState` should be done just in certain error cases, not always.

A situation where there are new ops meanwhile on the server is just to be expected in normal execution and nothing I would consider an error. It is a normal state conflict for which we have the OT do automatically resolve that.