Remove small local video.

Update when local vs. remote video is shown in the main window, and when the main remote vs. the small remote video are shown.

The local video should be displayed before another user joins, as well as when in calibrate mode. When a second user joins, the remote video is displayed in the main window, and when zoomed in far enough, switches to a small window in the upper corner.

Fixes #2454.
Mute local video.

Refs #2454.