replace deprecated escape() with encodeURIComponent()

Actually fix slide indexes.

While the page numbers from BigBlueButton are zero-based, the slide images
are generated as 1-based.

fixed the glowing listen only indicator

fixed 'zoom slider won't update value after presenter have changed'

Copy chat selection as text

Chrome webcam permission prompt

 - although the page number is not used in whiteboard recording processing, just match the page number with the goto slide event in events.xml

This was added because BigBlueButton 0.9 started using 1-based page
numbers in the events.xml file. That change has been reverted, so as
to avoid behaviour changes from 0.81 in places where it's unnecessary.

 - subtract 1 from GotoSlideEvent and ResizeAndMoveSlideEvent to events.xml so that the recording is backwards compatible with 0.81 and earlier

 - add current time on header of JSON messages so we can display the correct time instead of calculating from the timestamp

 - a meeting that has duration zero (runs infinitely) should be cleaned-up if no one has ever joined on it