This avoids the need to pass the username in the URL without
requiring the client to parse tokens.

Now that we support external auth, the permissions list is
open-ended.  Make it a list for simplicity.

It is now possible to autojoin by going to a URL such as

  https://galene.example.org/group/test?username=jch&token=...

This makes it possible to use token authentication without
an authentication server.

https://github.com/LucasReade/Contextual.js

Nice DTLS fixes in pion/dtls v2.1.2.

This was broken when we renamed status to data.  Thanks to
Sylvie Tissot.

This fixes an issue with non-simulcast tracks being discarded
when bundled with simulcast tracks.

More explicit data structures, better error handling.

Firefox implements the spec correctly by encapsulatings received
data in a blob by default.  Handle both blobs and ArrayBuffers.

Also improve error handling.

We now distinguish between status, which is maintained by the server,
and data, which is provided by the client.  In addition to client data,
we now support group data.

Setting the status after joining (using the "setstatus" action)
may cause multiple "user" messages to be sent to clients.  Add
the ability to set the initial status at join time.

Commit 993d66 addes support for displaying raised hands, but it
failed to take into account the possibility that the hand is already
raised when the user is first added.

We're already doing it in the receiver loop.

Doing that at the sample level suffers from too much delay
due to buffering in the samplebuilder.