Don't  use the prosody admin console, as it's disabled.

If `lsb-release` is not installed, an invalid entry is added to `/etc/apt/sources.list`, leaving apt in an unusable state

Applies Fcrancois's suggestion about tipping users where they can start testing.
Removes occurrences of jitmeet since the name is no longer in use.

Change some jitmeet references to Jitsi Meet and other minor cleanup.