* Make the roomserver output format more flexible

* Fix the sync server integration testdata

* Fix roomserver testdata

* Actually fix the sync server tests

* Fix typo

* Set depth of events and whether they need to be federated.

Set the depth of each new event to one greater than the maximum depth
of it's direct ancestors.

Add a flag to each event passing through the roomserver that tells us
whether the event needs to be sent over federation.

We do this by passing the name of the server to send the event as.
We will need this capability if we want to support vhosting as it is
not possible to tell from the event alone which server to send it as.

(The reason for this is that sometimes a event needs to be sent on
behalf of a different remote matrix server)

* Update roomserver integration tests

* More comments

* Constants and comments

* Fix comments

* Document the int64 returned by LatestEventIDs

* Include the state before the event in roomserver output

* Fix roomserver integration test

* Remove VisibilityEventIDs from the JSON

* More comments

* Remove spurious TODO

This should:
    1) Make the input package a bit cleaner.
    2) Allow use to reuse the state reading code from the query package.

* Add method for calculating the room state after a list of events

* Fill out AddsState and RemovesState fields in the output event

* comment on return value

* Fix whitespace

* Clarify the meaning of LastEventIDSent

* Be more explicit on what the snapshot is

* Fix comments

* Comment on why we want the state after the previous events

* Track which events have been sent and the last event sent for each room

* Write output events

* comment that an event could be sent twice

* Get the SQL working, and make it more idempotent

* Track which events are the latest events in the room.