The vertical alignment was being set with javascript.
Recent changes might make the setting of alignment exit
early due to height 0 video. As position can be set
declaratively with css, use css to set position.

* Updates start silent, turning on startWithAudioMuted and few UI tweaks.

Disabled mic unmute button and removes remote participants volume slider.

* Adds analytics for start silent.

* Removes extra semi colon.

* Updates lib-jitsi-meet and updates meeting info text.

This reverts commit 890151fa72.

For remote chat messages, all corners should be rounded
except the top left. For local messages all corners
should be rounded except the top right.

By making the container 100% height and position relative, that
would cause it to overlap any static-positioned  elements below it.
The 100% makes it so that any watermarks intended for the bottom
of the page show up on the bottom of the page. However, it's not
needed because watermark stylings already try to position the
watermarks at the bottom.

Otherwise it can eat clicks on elements it is above,
like YouTube and Etherpad controls.