Fixes #8252

Add an example to enable generating an mp4 file (Apple device compatibility)
Switch the webm generation to use the faster single-pass encode by default,
since 2-pass is much slower and more cpu intensive.

Adapt the screenshare processing script to changes to the api for events handling in
the recording-and-playback core libs.

I forgot to include the 'K' multiplier on the bitrate values, so they
were all 1000 times too low.