It is now possible to specify codecs other than VP8 and Opus.  This
turns out not to be very useful, since VP8 is the only codec supported
by all browsers (in violation of the WebRTC spec, which mandates support
for H.264), and there is no good reason to use anything other than Opus
for audio.

This avoids spurious up.complete indications.

This is not an issue in the current code, assuming that clients
negotiate correctly, but will become one once we implement codec
flexibility.

We used to push a connection when we got all tracks.  However, it may
happen that some tracks fail; in that case, the connection would never
get pushed.

We don't renegotiate down connections yet, but this is a latent bug.

If autoplay is not working on browser, user can play the video with this button

Reorganize radio buttons also.

No UI for now.

These functions require having joined a group, not just having
proper credentials.

Thanks to Antonin Décimo.

Co-authored-by: Juliusz Chroboczek <jch@irif.fr>

Reduce button size and reduce video control bar size.
Add a volume slider to control volume level when volume control is enabled

There is no text on mobile layout

This was causing us to lose connections.