Change back to the old, non-modular recording file format. The new
method doesn't work reliably and there are existing recordings already
out there that we might want to handle.
This commit makes vnc_playback.html functional once more, and completely
refactors tests/playback.js to make it usable in other scenarios.
In order for vnc_playback.js to properly load playback files now, they
must `export` their variables.
Pierre Ossman
Samuel Mannehed
Solly Ross