GUADEC 2020 moves to online conference

I’ve updated the scripts a bit to make it easier to split up the day-long BBB recordings. As an example, the Accessibility talk from the first day could be extracted with the following commands:

./ '' d1t1
./ --start=5194 --end=7200 d1t1 a11y.xges

[the start and end times are approximate: they should be adjusted as needed]

The a11y.xges file can be rendered to a video with ges-launch-1.0 as described in the README file. The make-xges script also takes a --backdrop argument that sets an image to place behind the slides and camera. This can be used to fill in some of the blank space and add some branding to the video.