Added waitForInitialSyncCompletion so that clients can know when they can access to the data retrieved by the initialSync Request

Support multiple login flows when deciding how to login. Updated cmdclient and spec. Webclient doesn't need updating for this.

Start the events stream once the app starts (if credentials are in cache) or once the user gets logged in

Conflicts:
	tests/handlers/test_federation.py
	tests/handlers/test_room.py

Conflicts:
	synapse/handlers/room.py
	synapse/storage/stream.py