Clarify that room alias domain names will be server-scoped; nonlocal edits are unliekly to work but nonlocal lookups will

Outline and describe the keys from the initial sync API. Hide room-scoped
initial sync API for now as it is not implemented and needs more thought before
it can be specced.

Currently, if you leave a room you still appear in the members list.
This is basically a bug with the current implementation/spec, rather
than something that should happen.

Continue moving content out of docs/model/presence into the main spec; delete model docs that are duplicated

SPEC-25 #comment I've added the details of what the server should do on
receipt of a redaction event. In reality it can do whatever it wants,
and its probably a reasonable implementation to flag it up to a server
admin for verification before actually redacting an event.

Move documented but-unimplemented 'presence idle times' into a new document to contain such features

Nuke the entire 'Typing Notifications' spec section given as they don't exist yet in the implementation