Split screen editing step 1!

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
* [ ] Add support for OT
* [ ] Pause/play support to interrupt flow between clients
* [ ] Quicker login?
* [ ] Let Bella loose in these!