Live presentation updates

[gerazov]

Currently the slides are parsed at presentation start and edits of the file break the presentation.

It would be nice if we could have live updates (useful for screen extended sharing).

Another level to this would be to be able to modify the slides and for it to update the buffer (useful for duplicate screen sharing).

[sotte]

I agree, this would be nice!

I'm not sure how to implement something like it while keeping the code base small. Suggestions welcome!