Attempt to move room aliases on room upgrades

Fix typo in docker-compose.yml

I found these helpful in debugging my room upgrade tests.

Attempt to fix tox installs

Signed-off-by: Jonas Schürmann <jonasschuermann@aol.de>

It seems that, at some point, the ability to run tox on old servers (with old
setuptools) got broken - and it was only working on our Jenkins instance by
dint of reusing the tox environments.

Let's try to get tox to do the right thing, and remove the guff from
jenkins/prepare_synapse.sh.

(There is a separate question about whether the jenkins builds should be using
tox to prepare the virtualenv at all here, but that is somewhat orthogonal).

 Delete unreferenced state groups during purge

A couple of replication fixes for device lists

Erikj/repl names

We currently send several kHz of device list updates over replication
occisonally, which often causes the replications streams to lag and then
get dropped.

A lot of those updates will actually be duplicates, since we don't send
e.g. device_ids across replication, so let's deduplicate it when we pull
them out of the database.

Remember to copy the avatar on room upgrades

Better handling of odd PLs during room upgrades

Room version upgrade support

Fixes handling of rooms where we have permission to send the tombstone, but not
other state. We need to (a) fail more gracefully when we can't send the PLs in
the old room, and (b) not set the PLs in the new room until we are done with
the other stuff.

Improve comments, get old room state from the context we already have

This test stubbed out some stuff in a very weird way. I have no idea why. It broke.

Make Docker image listen on ipv6 as well as ipv4