Use the last user display name

More formatting, more TODOs. Settled on a way of linking to external API docs; started converting references to relative links.

spec: Added internal links to different sections. Added NOTE and WARNING admonitions and hide away loooong TODO lists behind comments. Smaller ones remain.

Updated howto.rst to use the new APIs. Updated JSFiddles to use 8008. Linked new fiddles with howto.rst. Added more explanations.

Conflicts:
	synapse/notifier.py
	webclient/room/room-controller.js
	webclient/room/room.html

AngularJS will instantiate it when discovering ng-controller in their respective html files

Represent user power level in a room by a red bar at the bottom of his avatar image. The width of this bar depends on the power level.

Make the intro bit a separate section rather than have a 'quick start' section that only tells you how to get started half way through.